[HN Gopher] What a year of solar and batteries saved us in 2025
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What a year of solar and batteries saved us in 2025
Author : MattSayar
Score : 227 points
Date : 2026-01-13 15:49 UTC (7 hours ago)
(HTM) web link (scotthelme.co.uk)
(TXT) w3m dump (scotthelme.co.uk)
| kccqzy wrote:
| Good analysis. And kudos to the author for saving money. But
| still 21.6MWh per year excluding solar production seems too high
| for a household. I use electric heating and drive an electric
| vehicle, and my household annual energy consumption is about one
| fifth of that.
| louwrentius wrote:
| From the article: "My wife and I both drive electric cars"
|
| That probably explains it.
| lostlogin wrote:
| A single extra charge in a month can really mess the stats
| up.
| vel0city wrote:
| An average EV battery is what, around 70kWh? Add in a bit
| of charging losses and we'll say _maybe_ 75kWh being
| generous here, and that 's assuming a nearly dead battery
| to a full charge. Doing that every month is then 900kWh, or
| 0.9MWh/yr. That's ~4% of the energy usage of 21MWh/yr.
|
| An average EV gets what, ~3.5mi/kWH? An average US car does
| ~12,000mi/yr. That theoretical average EV would then use
| ~3.5MWh. Two would be ~7. But this author is in the UK,
| where the average car only does ~7,500mi/yr or so or a
| little over 2MWh/yr. So for their two UK cars, assuming
| they drove an average mileage in an average EV efficiency,
| they would likely have used something like 4.3MWh/yr for
| their cars. About 20% of their total electricity usage.
| This drops a good bit if they're really getting closer to
| 4mi/kWh in efficiency, which is likely if they're not
| driving on many highways like one does in the US.
| metadat wrote:
| EV charging inefficiency typically loses 10-25% of the
| input energy, depending on temperature and battery level
| (low temps are bad, very low or high battery level also
| bad for efficient transfer).
| lostlogin wrote:
| That percentage of total usage is tiny, I agree.
|
| We have one car and charge it quite often.
|
| I just checked last month: 184kwh went into the Leaf. We
| used 557kwh in total (excluding the car charging).
|
| We generated 1170kwh.
|
| The key thing for me is the wild energy usage from the
| house. It's a lot.
|
| Edit: Your car energy usage calculation works out awfully
| close to what we use.
| kccqzy wrote:
| Yeah but they both work from home. The biggest reason for
| putting mileage on the car, commuting, is now out.
| bryanrasmussen wrote:
| maybe saving money they used more - in other words Jevon's
| paradox https://en.wikipedia.org/wiki/Jevons_paradox
|
| thus perhaps leading to more global warming
| Aboutplants wrote:
| That's about double the average household so I would imagine
| spending that money and effort into energy efficiency would pay
| off way better that solar and batteries.
| lm28469 wrote:
| The average household doesn't have two electric cars though
| pixl97 wrote:
| Yea, averages don't work well when talking about single
| units without any further details.
|
| How many sq/ft is the house?
|
| Is it filled with windows facing south?
|
| Are they firing a continuous laser beam at the moon?
|
| 2-3x usage is actually pretty typical when looking at a
| single house when comparing to average. It's when you start
| getting close to an order of mag difference that you're an
| outlier.
| KaiserPro wrote:
| I have an electric car, one powerwall (pre musk midlife
| crisis) and 5kw solar. we consumed 6mwhrs in 2025. Gas
| heating and hotwater, about 190w base because of
| networking, servers and shit left on.
| Scott_Helme_ wrote:
| How did you know about my laser?!
| icehawk wrote:
| 20MWh is around what my house used in both 2024 and 2025.
| davely wrote:
| This number can mean wildly different things depending on the
| size of your house (and location).
|
| I live in the Bay Area, CA in a 1,500 square foot house and
| consumed 7.8MWh in 2025 and 7.6 MWh in 2024.
|
| Digging a bit more into our solar system data: We produced a
| bit over 9MWh in solar each year and it looks like our
| Enphase batteries discharged 2MWh each year.
| lostlogin wrote:
| I can't see any mention of hot water or cooking in the article,
| which may be relevant.
|
| I was stoked at the power saving from turning off an espresso
| machine a bit sooner, a swapping out a nuc to a Mac mini.
|
| Maybe there is a bit coin mining operation in his basement?
| Scott_Helme_ wrote:
| Nah, there's no Bitcoin mining, honest!
| cptcobalt wrote:
| Not all homes are made equal: different appliances &
| electronics from different vintages, etc.
|
| I have 2 EVs (Tesla and BMW), an electric oven, and a homelab
| rack (but no HVAC), and my usage was 34.4 MWh last year -- with
| 100% from Solar and Powerwall.
| lostlogin wrote:
| That's an awful lot of power.
|
| I'm waiting on a quote for an hvac that uses its waste heat
| for the home hot water. Im irritated that I'm cooling the
| house, pushing out hot air, and heating water at the same
| time.
| sponaugle wrote:
| On that avenue, I do push hot air from my homelab into my
| upper garage for heat. If it below 50deg outside I also
| bring in some cold air from outside. Both are somewhat free
| offsets for heating/cooling.
| lm28469 wrote:
| Get a basic heat recovery unit, it basically has no moving
| parts (just a few fans) and good ones recover 90%+ of the
| heat going out of your house. It's almost useless if you
| don't have an airtight envelope though.
|
| All in one systems with water heating are way too complex
| and _will_ fail relatively quickly, mini heat pumps won't
| last 10 years, and by the time it dies you won't be able to
| find a replacement for your specific model
| lostlogin wrote:
| This makes me sad. I'm in a 1940s house where the lack of
| it being airtight is a key reason it's still standing as
| it leaks and the airflow dries it. Water flows down the
| inside of the brickwork, and the cavity is well
| ventilated.
|
| Yay for New Zealand housing.
| MisterTea wrote:
| > All in one systems with water heating are way too
| complex and _will_ fail relatively quickly, ...
|
| Can you offer some evidence of this? I don't see how
| adding a refrigerant to water heat exchanger after the
| compressor, before the reversing valve, could possibly
| hurt the longevity of a system.
|
| > ... mini heat pumps won't last 10 years, and by the
| time it dies you won't be able to find a replacement for
| your specific model
|
| Thing with mini-splits is you replace the entire unit so
| it doesn't matter.
| lm28469 wrote:
| > Can you offer some evidence of this? I don't see how
| adding a refrigerant to water heat exchanger after the
| compressor, before the reversing valve, could possibly
| hurt the longevity of a system.
|
| The nearly infinite amount of forum posts about heat
| pumps dying prematurely and costing thousands and
| thousands to fix. You don't see how adding complexity on
| top of complexity in a complex system add points of
| failures ?
|
| > Thing with mini-splits is you replace the entire unit
| so it doesn't matter.
|
| I forgot this is an american centric forum and things are
| just made cheap/disposable because "it's cheaper'
| kccqzy wrote:
| You just need an air source heat pump water heater and
| install the water heater next right to the outdoor unit for
| the HVAC.
| sponaugle wrote:
| I used about 64MWh last year, not counting what I used for EV
| charging (Which is on a separate meter). I also produced about
| 20MWh from Solar. With the EVs I would guess the total is
| around 70MWh.
|
| Some of this extra is certainly my 6kw homelab + HVAC for that.
| ;)
| micromacrofoot wrote:
| I'm an example more towards the middle.
|
| In 2025 I produced 6.5MWh (solar) and consumed 12.7MWh
| (excluding solar production); this is a family of 4 in a 4
| season climate with electric heating and a single electric car.
|
| That was my highest year over the past 5 years.
|
| An additional EV can really add up, especially if both people
| have long commutes.
| kccqzy wrote:
| They have no commutes. They both work from home. I don't even
| understand why they need two cars for that.
| bz_bz_bz wrote:
| Their total household usage was actually ~17.3 MWh depending on
| what data source you're using for their usage.
|
| Given 6 MWh of exports with only 3.2 MWh of total solar
| production, they are cycling their powerwall to get paid for
| the fact that their off-peak rate is half the price of their
| peak export tariff rate which is inflating the number you're
| looking at.
| UltraSane wrote:
| That is still an enormous amount of electricity for a single
| family to consume.
| Dylan1312 wrote:
| It's less than 50kwh a day, high but seems reasonable with
| 2 electric cars.
| Aromasin wrote:
| He mentions that he has a server. It wouldn't surprise me
| if that consumes the majority of that.
| port11 wrote:
| People need to stop using the old Mac Pros for home
| servers, jeez.
| darknavi wrote:
| I had a old, cheap, used Dell R710 that I bought used in
| ~2016 until 2025. It only took a few months of running a
| new, much more efficient server to pay for its self.
| DamonHD wrote:
| We brought down our energy consumption substantially over the
| years starting not so far from that high figure, including
| swapping out racks of Sun servers for an RPi or two, and we are
| now slight net exporters of utility energy and with it roughly
| zero carbon...
|
| https://www.earth.org.uk/saving-electricity.html
| lm28469 wrote:
| It's high but it really depends on your lifestyle and
| appliances.
|
| If you have a heat pump water heater and heat pump based floor
| heating you'll use 1/4th of the energy as the same house with
| resistive water/floor heating.
|
| A house which barely passed regulation from 2010 will consume
| 5-10x the energy of a certified passive house.
|
| etc.
|
| That being said I think you have to draw the line somewhere.
| I'd much rather have inefficient appliances (resistive
| boiler/heaters) and be fully solar powered than spend 50k in
| heatpumps and other gimmicks that are rated for 10 years and
| cost a kidney in maintenance and the eventual replacement.
| rokkamokka wrote:
| Heatpumps are not a gimmick - they're an excellent technology
| with lots of efficient and effective uses :)
| lm28469 wrote:
| Overly complex and fragile in the long run, the savings are
| meaningless if you're already self sufficient. I'd much
| rather spend the money in insulation and self sufficiency
| than these voodoo appliances.
|
| That's my reasoning my new build house with plenty of land.
| In other scenarios it might be more beneficial to go for
| them.
| UltraSane wrote:
| Heat pumps are no more fragile than air conditioners.
| lm28469 wrote:
| Yes, and that's why I have none.
| mrspuratic wrote:
| No fridge? That's a heat pump.
| RussianCow wrote:
| Not everyone lives in an area where they can afford not
| to have one, especially with climates changing and
| temperatures hitting higher/lower extremes.
| lm28469 wrote:
| It all comes down to building techniques, insulation,
| airtightness, eliminating thermal bridges, &c. There are
| also many low tech solutions for heating/cooling, such as
| air/air heat exchanger couples with ground/water or
| ground/air heat exchanger at a fraction of the price and
| a fraction of the maintenance.
|
| Of course the average american living in a mcmansion
| which wouldn't pass regulations in 1992 Poland cannot use
| such solutions, but really it isn't a problem of climate,
| you'll find passive houses from africa to norway and
| everywhere in between, most of them without heat pumps
| dahfizz wrote:
| Which are famously reliable and cheap to service...
| fastasucan wrote:
| Thwre is nothing voodoo about heat pumps. Not really that
| complex and not at all fragile either.
| subroutine wrote:
| Heatpumps, Shmeetpumps
| pjc50 wrote:
| Heatpumps can now be had for less than PS10k .. if you don't
| have to replace your radiators.
|
| I do think more people should consider mini-split reversible
| AC in the UK, but the subsidy system specifically excludes
| it.
| ZeroGravitas wrote:
| UK government subsidy support for air-to-air was announced
| a couple of months ago:
|
| https://www.gov.uk/government/news/discounts-for-families-
| to...
| BeetleB wrote:
| Who spends $50K on heat pumps? They're not anywhere near that
| expensive.
| lm28469 wrote:
| I'm talking about geothermal water/water installs for
| central heating.
|
| No one is heating their place with air/air heat pumps
| besides americans who haven't figured out that heating
| spaces via air is shit tier in term of comfort and
| efficiency
| Retric wrote:
| Having one place to handle humidity, temperature, and
| exchange of fresh air makes ductwork the king of comfort
| and efficiency.
| lm28469 wrote:
| Separation of concerns is the king of avoiding pricy
| maintenance and headaches.
|
| You can already do most of that with a passive heat
| recovery ventilation system coupled to a ground/water
| exchanger. All systems are independent and the most high
| tech equipments you need are fans and a water pump
| Retric wrote:
| It's a tunnel for air.
|
| Only using ductwork for heat recovery ventilation without
| also using it for heating and cooling means more
| complexity, instillation costs, and maintenance issues
| etc. Further moving air allows you to use dramatically
| less material for heat exchangers.
|
| Net result higher efficiency, fewer things that can
| break, fewer locations something can break, and lower
| risks of water damage to your home etc.
| UltraSane wrote:
| says the guy calling heat pumps "voodoo appliances"
| lm28469 wrote:
| I forgot HN doesn't understand humor, I'll try to turn it
| down next time my bad.
| zdragnar wrote:
| When your annual temperature range is -40 to 40 C (or a
| bit over 100 F) central air HVAC is a life saver.
| doikor wrote:
| > No one is heating their place with air/air heat pumps
| besides americans who haven't figured out that heating
| spaces via air is shit tier in term of comfort and
| efficiency
|
| At least here in Finland a lot of people do. Very popular
| choice when replacing old oil furnaces (and as a
| "replacement" for direct electric heating offcourse)
|
| Geothermal heatpump is something people mostly think
| about when building new.
|
| Air heatpumps with the inside unit start from around
| 1000EUR and 300EUR to 500EUR for the install. The price
| is mainly based on the size of the house (and in big
| houses you will need multiple or one with multiple inside
| units)
|
| A fireplace for the couple really cold weeks to cut down
| the electricity bills are popular but people had those
| even before the air heatpumps so nothing new really.
| fastasucan wrote:
| >No one is heating their place with air/air heat pumps
| besides americans
|
| I am, and I am not an american, lol.
| coryrc wrote:
| A lot of people in America, sadly. Mini splits cost $250 to
| install in Japan and frequently $10k/head in the USA.
| Barbing wrote:
| >heatpumps and other gimmicks
|
| Anecdotally, two of the smartest people I know love heat
| pumps--doesn't Technology Connections too?
|
| Was probably this: Heat Pumps: the Future of
| Home Heating
|
| https://youtube.com/watch?v=7J52mDjZzto
| lm28469 wrote:
| It depends where you live, where you get your electricity
| from, for how much, &c. It's an amazing tech don't get me
| wrong, and of course youtube tech nerds love these kind of
| things, no surprise here, I just don't think it's the
| silver bullet everybody imagine it is.
| hattmall wrote:
| Heat pumps aren't particularly expensive though and they can
| provide cooling.
| youngtaff wrote:
| I think Scott's usage is high - I think he mentions between
| PS300-400 / month - but then he's got a hot tub, server rack as
| well as the cars.
|
| We still have an ICE car and gas central heating but our
| combined electricity and gas bill is around PS140 / month
|
| Plan to go to EV and heat pump in our next house though
| KaiserPro wrote:
| external wall insulation and triples glazing first! We did it
| and made winter ~10 degress warmer, and summer 15 degrees
| cooler. its cheaper than the solar/battery install.
| HexPhantom wrote:
| It's more a stress test showing that even with unusually high
| consumption, solar + batteries + tariff optimisation can still
| materially change the cost curve
| GordonS wrote:
| I was really surprised too - our family (with electric car and
| a lot of tech) uses only a third of the energy used in TFA!
|
| Still, even with our lower usage, solar still makes sense
| (especially with a South-facing roof) because electricity is so
| damned expensive in the UK :(
| sounds wrote:
| The US clean energy tax credit is only available for equipment
| installed on or before Dec 31, 2025 https://www.irs.gov/credits-
| deductions/residential-clean-ene...
|
| As a result, more used solar should become available on ebay. I'm
| excited to see what I can do on a shoe string budget.
| willis936 wrote:
| Don't be surprised when the answer is "not much". Apply supply
| and demand to electric power generation. If your grid rate is
| getting hiked then so is the market price of used solar.
| IAmBroom wrote:
| Assuming the entire used market is efficient, which I doubt.
|
| There will at least be a lag.
| toomuchtodo wrote:
| Battery storage tax credit (30%) runs through 2032, must have
| at least 3kwh capacity. IRS Form 5695.
|
| https://www.energystar.gov/about/federal-tax-credits/battery...
| lm28469 wrote:
| Why do people still go for tesla powerwalls when you can get BYD
| batteries with 70%+ more capacity for cheaper ?
|
| You can buy a BYD HVM 22.1 kWh for 6000 euros now (PS5200) vs
| powerwall 2 13.5kwh for 7000 euros.
| pja wrote:
| Brand trust?
|
| (Yes, yes: insert Musk related joke here.)
| f1shy wrote:
| Those batteries must be connected to the internet to work,
| and the company could disable them anytime. Same for most of
| the inverters. I'm just hoping they don't pull some nonsense
| like we have seen with other "cloud" devices. In that sense,
| I trust Tesla as much as BYD, and that is not at all.
| flakeoil wrote:
| Or you can by a car instead. An MG4 costs less than 20000 euros
| with a 51kWh LFP battery. In addition to a good battery, it's a
| great car as well.
| lm28469 wrote:
| afaik it doesn't support bidirectional charging, I'd much
| rather cycle my standalone lifepo4 bank than my EV battery
| flakeoil wrote:
| Yes, it does. I haven't tried it as a do not have the cable
| for it, but the user interface for discharge is there and
| the manual also talks about this feature.
|
| It's probably not ideal for running a full house (as it
| would require some other electronics and installations),
| but a couple of appliances should work.
| ok_dad wrote:
| There are several types of bidirectional EV charging, the
| one most cars has is about a 1kW fused connection called
| "Vehicle to Load (V2L)" but the one you are discussing is
| what they call "Vehicle to Grid (V2G)" and in those cars
| it supports the full input and output of the vehicle
| inverter.
| f1shy wrote:
| In germany was (still is) illegal to use the car as
| battery... it is going to change soon though
| jstsch wrote:
| Battery prices are getting really low, if you're willing to do
| some DIY. Just received a 15kWh battery from China. A 'Humsienk'.
| Combined it with a GroWatt SPA3000TL-BL inverter.
|
| Total price, 1600 euros. So close to the magical 100 euros per
| kWh. Driving it with some interesting combinations of Raspberry
| PI's and serial interfaces and custom written Go code, but it
| works... :)
| j2kun wrote:
| I do wish I could have a good, in-depth tutorial on how to set
| this up myself. Along with (pipe dream) an explanation of how
| it would interact with my local utility. I worry that due to
| some silly technicality, I won't be able to export to my local
| utility, or else I won't be able to run off-grid when there's
| an outage.
| jstsch wrote:
| I will do a write-up in a couple of days. It's all relatively
| simple, you just have to expect terrible documentation and do
| a bit of reverse engineering and serial sniffing. I expected
| the battery to be complicated, but it turned out that the
| inverter was.
|
| You'll encounter stuff like: manual says use RS485 port on
| Battery for GroWatt inverter - need to use CAN port on
| Battery. Meter Port (RS485 [serial] over RJ45) wiring on
| GroWatt is unknown (A: white orange / B: white blue, cross
| them over). Dinky RS485 serial - USB converter needs a 120ohm
| resistor between pins for line termination. Growatt meter
| port expects a SDM630 meter, not a DTSU666 (hardcoded), so
| vibe code another emulator. DIP switches for RS232 connection
| need to be both on the ON position (undocumented). CH340 USB-
| serial converter for RS232 does not work, but one with a
| Prolific chip does. Etc. etc. etc :)
|
| Oh, and the biggest one... I was expecting to be able to just
| send a command, 'charge at 500watts', now... 'discharge at
| 2000watts'. But no. You have to emulate a power meter and the
| inverter will try to bring the net power to 0. Fun! :)
| rmcpherson wrote:
| I would appreciate this write up as well. Looking to do a
| DIY setup.
| f1shy wrote:
| > Battery prices are getting really low, if you're willing to
| do some DIY.
|
| Willing and allowed. In some countries it can only be done by
| certified electricians.
| pjc50 wrote:
| UK considerations: must be at least signed off by an approved
| electrician ("Part P" regulations), and for any situations
| involving subsidy needs to be MCS approved as well.
| https://mcscertified.com/
| ozlikethewizard wrote:
| Surely it only needs to be signed off if you intend to sell
| the property with them or sell excess back to the grid. If
| youre just using the batteries how is anyone going to know?
| pjc50 wrote:
| _shrug_ if you can rely on nobody noticing, or non-
| enforcement, sure, but it is actually a criminal offence
| not just an administrative requirement.
| aniviacat wrote:
| I'd assume your fire insurance covers nothing if
| illegally installed batteries are found inside after a
| house fire.
| baq wrote:
| If your house burns down for any reason, not necessarily
| the DYI batteries, the insurance company will know
| anyway.
| dns_snek wrote:
| If the DIY work wasn't the cause for the fire it
| shouldn't matter, but I half-expect someone to inform me
| that US insurance companies can (legally) deny coverage
| for reasons unrelated to the accident.
| buckle8017 wrote:
| How are you going to absolutely price that the batteries
| didn't start the fire or even just make the fire worse?
|
| You can't and you will lose in court.
| dns_snek wrote:
| I wouldn't have to, where I'm from the burden of proof is
| on the insurance company.
| MisterTea wrote:
| Find an electrician who will inspect and sign off on your
| work. It's not illegal as licensed master electricians have
| mechanics do all the grunt work who are unlicensed. The
| electrician vouches for his employees work which
| legitimizes it. No different than you doing the work and
| having the electrician inspect, call out issues to fix, and
| inspect again until no issues are found and sign off.
| scarecrowbob wrote:
| I mean, it "can" be done without a certificate.
|
| It "may" not be permitted, but if you live in a collection of
| shacks in rural Colorado that were themselves -already-
| completely un-permitted then you might decide that it's best
| to just do the work yourself.
| MisterTea wrote:
| Then pay one to inspect it and sign off for you.
| testing22321 wrote:
| I paid an electrician one hours work to actually connect my
| inverter to my main 200A panel, and he even got the required
| building permit required.
| Barbing wrote:
| Awesome.
|
| Feel you have more unknowns on the safety front? vs. the
| expensive off-the-shelf. [in the USA, it'd also be "fewer names
| to sue" in that unlikely tragedy of combustion in home, but no
| _euro_ /kWh targets there]
| tomashubelbauer wrote:
| LFP batteries are as likely to burn down your house as a
| stack of wood is. I'd be worried about the inverter or
| botched DIY wiring (especially not to spec torque on terminal
| connections and botched crimps leading to hot spots), but not
| about the batteries themselves. For a person who wants to
| save some money, but doesn't know how to work with
| electricity, the best move is probably to get cheap LFP cells
| from China, but have a professional install a BMS and the
| remainder of the solar system.
| jstsch wrote:
| > especially not to spec torque on terminal connections and
| botched crimps leading to hot spots
|
| This was indeed my greatest concern. However the battery
| came with pre-crimped very solid DC wires, and nice push
| connectors for the battery itself. The battery also has an
| integrated DC breaker (great!).
|
| The system runs 3KW max, so I just added an additional
| breaker (with RCD integrated) in the conduit box. In NL
| this is something a DIY-home owner easily can do themselves
| :) (just use the right solid/flex stranded cabling for the
| connectors, etc...)
| scarecrowbob wrote:
| And further, my position has been that learning the
| correct methods, paying a lot of attention to details,
| and not being cheap with tools is -still- cheaper and
| probably more reliable than paying contractors. I have
| only used my hydraulic crimper for a pair of cables, but
| it was the correct tool and did good work.
|
| I'm not interfacing with a grid, and there are already
| code issues with my places- I'd probably feel different
| if I could get insurance on my place.
|
| Cheap chinese tooling and youtube (plus pretty good
| general literacy) go a long way in this world.
|
| And FWIW, I live in the US west and am way more worried
| about fire coming from outside than from the batteries.
| milesvp wrote:
| > botched crimps
|
| On a tangent, I'm amazed at how bad most random crimps I
| see on the internet are. Also, the number of people who
| debate the use of solder on crimps without discussing
| potential issues with said solder is too high.
| Aurornis wrote:
| > LFP batteries are as likely to burn down your house as a
| stack of wood is.
|
| LFP batteries are much safer than past chemistries, but
| this statement is way too broad.
|
| High power batteries are always more dangerous than
| something like a stack of wood, because batteries will
| gladly dump their entire energy capacity very rapidly into
| a short.
|
| Even if the battery itself [mostly] won't self-immolate,
| the entire installation can be a fire hazard.
|
| Treat them with proper respect.
| ViewTrick1002 wrote:
| We are finally starting to see Chinese prices externally.
|
| It's been crazy seeing the western home storage market selling
| systems with the EUR/kWh being more expensive than buying a
| BEV. And that includes a car.
|
| https://www.docanpower.com/eu-stock/zz-48kwh-50kwh-51-2v-942...
| Dylan1312 wrote:
| Did the same, got a solar installer to fit panels on garage and
| a solis hybrid inverter. They fitted a CT clamp on my meter and
| a lora device on both sides for it to communicate with the
| inverter.
|
| Then bought a 16kwh battery for ~PS1500, installation was
| plugging in a positive, negative and ethernet cable and
| configuring the inverter to use the battery. (if my home
| insnurer is reading this, I had an electrician friend double
| check while helping with some other work)
|
| Definitely recommended for anyone who likes tinkering,
| thousands cheaper than installer pricing.
| microdrum wrote:
| Yup, Growatt is the Chinese OEM that Base Power white labels to
| pretend it does US manufacturing. In fact this stuff is low
| quality. You need to be careful. There are gradations of
| quality at cell, pack, inverter, control levels. You will be
| crushed if you realize you AliExpressed your way to a home
| power "solution" only to have it fail young.
| MisterTea wrote:
| > Driving it with some interesting combinations of Raspberry
| PI's and serial interfaces and custom written Go code, but it
| works... :)
|
| What protocol is it speaking? I've seen some of the more
| mainstream models call out that they use Modbus but all the
| cheap import models either might use Modbus or some custom
| protocol you have to reverse engineer or hope someone else did.
| Havoc wrote:
| Recently switched to octopus too because they have a proper api
| with 30min consumption updates
| apercu wrote:
| My electric bill was up 35% year over year from 2024 to 2025 -
| only two of us live here and there were no infra changes or new
| appliances.
|
| I really need a solar solution but I feel so far out of my
| wheelhouse.
| drak0n1c wrote:
| I had a good experience using EnergySage, a free marketplace
| that sources competitive detailed bids - it just needs your
| address and electric bill.
| toomuchtodo wrote:
| https://solarunitedneighbors.org/help-desk/
| elAhmo wrote:
| Great read!
|
| I am just wondering would stacking up batteries, charging them
| off-peak and using/selling back during peak usage be as good as
| this, or even better? Seems like this shouldn't be a viable
| scenario, but given the prices and idle capacity, it seems just
| investing in batteries and charging them at night, to be
| used/sold to the grid during the day would be as good as a solar
| installation.
| cptcobalt wrote:
| You can usually save more by generating solar locally and using
| it to power the home and charge the battery, then discharging
| the battery during peak hours (usually around and just after
| sunset) to earn the most. Obviously higher upfront capex.
|
| Pure grid cycling is also frowned on by some utilities.
| DamonHD wrote:
| Octopus in the UK has tariffs where it basically takes over
| your system (ie the batteries in particular) and subsumes
| them into its wider activities, eg:
|
| https://octopus.energy/intelligent-flux-faqs/
| pixl97 wrote:
| >it seems just investing in batteries and charging
|
| I mean a lot of companies already do this with
| megawatt/gigawatt installations.
|
| The key is peaking and grid stabilization. If you're a huge
| provider you can pay for all your batteries in a year or two if
| there is some large grid emergency and rates skyrocket.
|
| If you're a non-commercial user, it's going to be hard because
| the provider rates you pay/get paid are much more likely to be
| fixed at a pretty low rate.
| icegreentea2 wrote:
| The author pays PS0.07/kWh off peak, but can export at
| PS0.15/kWh. The author paid ~PS7500 per powerwall which has
| ~13.5kWh capacity. Assuming full charge/discharge every night,
| you can make ~PS1.08 per day, which works out to about 19 years
| to pay back.
|
| Utilities normally consider disincentivizing this type of
| behavior from residential customers as one of the factors when
| setting their export pricing.
| Scott_Helme_ wrote:
| We had an expensive solar install due to restrictions around
| our roof, so the solar would typically have been cheaper.
|
| Another consideration is that battery installations in the UK
| are charged at 20% VAT, but if they're installed as part of a
| solar installation, they're charged at 0% VAT. So even if your
| main interest is in getting the batteries, a small solar
| install might make sense because of the savings.
| malchow wrote:
| You can add your car to your whole-house AC bus using the Enphase
| bi-di EVSE, releasing this year:
|
| https://enphase.com/ev-chargers/bidirectional
| boringg wrote:
| 9-11 year payback isn't bad based on the projections. You could
| probably goose it a bit with inflation of electrical prices
| (depends on how the electrical policies change and what they pass
| through).
|
| I'll also add theres some O&M coming down the line. Inverters @
| year 10, small maintenance and Im assuming you re-did your roof
| before you installed. Anyone putting solar up make sure you do it
| at the same time as a roof because taking it down to redo a roof
| kills your economic value.
| toomuchtodo wrote:
| It is essentially a bond return, with the caveat being that
| solar PV panels will last 25+ years with some degradation and
| reduction in output. To your point, the best arrangement (imho)
| is a standing seam metal roof (40-70 year lifetime) with the
| panels mounted via friction racking with no roof deck
| penetrations. This avoids the economic cost of pulling
| everything off the roof to re-roof, and should outlive any
| homeowner 40 years of age or older. I also expect labor willing
| to get on a roof becoming more scarce and expensive over time
| in the developed world, which I think should be taken into
| account. Your battery storage can be replaced 10-15 years from
| now at the end of its service life by anyone with a hand truck.
| systemtest wrote:
| -
| toomuchtodo wrote:
| This is factually inaccurate. Solar PV panels will continue
| to produce power at 80-90% of rated output after 25 years,
| and battery storage will still have 80-90% capacity. I'm
| sure you can understand that as long as the system is
| storing and producing power at these levels, its value is
| not zero.
| systemtest wrote:
| Can you point out what part of what I said is factually
| inaccurate?
| toomuchtodo wrote:
| https://magnifina.com/articles/rooftop-solar-yield/
| explains it better than me attempting to write a wall of
| text.
| triceratops wrote:
| > while the initial principal of your bond investment will
| remain intact.
|
| As long as the bond issuer remains solvent. How much do you
| trust bonds that yield 9% to retain their full value for 25
| years?
| systemtest wrote:
| Don't buy junk bonds. Why are you looking for bonds that
| yield 9%?
| triceratops wrote:
| From the article:
|
| "Another way to look at this is that the investment is
| returning ~9%/year."
| systemtest wrote:
| That is without accounting for depreciation of the
| installation.
| triceratops wrote:
| How do you measure the depreciation? The panels deliver
| at least 70%, but probably closer to 80%, output after 25
| years. The batteries need replacing after maybe 15 years.
| Assuming that knocks a couple percent points off the
| return (batteries can only get cheaper and cheaper)
| that's still a solid 7% long term yield with no default
| risk. Share your math if you disagree.
|
| EDIT: Two more things that will juice the return
|
| 1. Grid electricity prices will go up over those 25
| years, at the very least tracking inflation.
|
| 2. Unlike bond coupon payments, the "return" from a solar
| installation isn't taxable. Because you're saving money,
| not getting paid.
| pjc50 wrote:
| > I'm assuming you re-did your roof before you installed
|
| In the UK I would expect the roof to be tile, which lasts
| basically forever unless a storm hits hard enough.
|
| I did have to have my panels taken down and refitted, at a cost
| of well over PS1000, because I hadn't bird-proofed underneath
| them (wasn't suggested by original installer). So watch out for
| that one.
| KaiserPro wrote:
| Yeah I need to un pigeon the underneath of mine.
| rv3392 wrote:
| How do you bird-proof them?
| vasco wrote:
| Almost all simulations I've done across 3 countries with 3
| different payback models for selling back to grid (one of the
| three doesn't allow selling back almost anything above your
| consumption), I could never make investing in Solar not being a
| gamble.
|
| You really need to gamble on odds of replacing equipment being
| very low for it to make sense. And in practice most people I
| anecdotally know that run it, after 5-7 years have already done
| additional purchases. The payback time keeps getting pushed
| back to the point that when payback will happen your panel will
| be worthless in efficiency compared to new ones. At industrial
| / commercial scale it makes sense, but humans like to move
| houses, and do stuff in the houses and that messes with the
| payback plans at the individual level.
|
| So either I was in the wrong countries or most people just
| gamble on the equipment lifetime, but for that I'd rather buy
| SPY calls, less drama.
| latchkey wrote:
| Having power when your entire neighborhood is off, priceless.
|
| [edit: yes, I assume you also get batteries, I know that
| solar alone doesn't magically power your house.]
| mattmaroon wrote:
| Well there are other, far cheaper ways to get that.
| boringg wrote:
| Whats funny about that -- is you assume thats the case -
| but a lot of solar isn't installed to be backup power. With
| Storage yes, but straight up solar -> no.
| dns_snek wrote:
| It's not the default but you can get it installed that
| way or get it adapted later (less than ideal if you end
| up having to replace the inverter).
| latchkey wrote:
| Yea, that costs extra. My dad went for the natural gas
| generator.
| dymk wrote:
| 99% of systems are grid tie, so unless you're spending
| another $7k for an ATS and associated infrastructure or
| you're 100% off grid, your power still goes off.
| IAmBroom wrote:
| For others who aren't up on the lingo:
|
| "An ATS (Automatic Transfer Switch) for solar is a
| crucial device that seamlessly switches your home's power
| between the utility grid, your solar panels/battery
| bank...
| dymk wrote:
| And I should clarify that you technically can get away
| with a less expensive interlock system, but you're still
| paying a few thousand dollars to have your panel replaced
| (unless you feel comfortable doing that sort of
| electrical work yourself).
|
| Making a system non-grid-tie is comparatively expensive,
| that's why grid tie is so common. People think you add
| solar + batteries and you're ready for doomsday - not
| quite.
| vanc_cefepime wrote:
| Outside transfer switch and a 10-20kw portable generator is
| like $4-5k. It requires manual switching but it works for
| us in our hurricane-prone region. Helped with last years 1
| in a 100 year winter storm in our southern region.
|
| Battery/solar doesn't make sense in my opinion. Too many
| years to break even like this parent comment said and by
| the time you break even at 10 years, your system either is
| too inefficient or needs replacing. At least with the
| portable generator, you can move it with you to a new home
| and use it for other things like camping or RVing.
| hectormalot wrote:
| Context: I'm in the Netherlands. With taxes, power is
| around 25cent/kWh for me. For reference: Amsterdam is
| around a latitude of 52N, which is north enough that it
| only hits Alaska, not the US mainland.
|
| I installed 2800Wp solar for about EUR2800 ($3000,
| payback in: 4-5 years), and a 5kWh battery for EUR1200
| ($1300) all in. The battery has an expected payback time
| of just over 5 years, and I have some backup power if I
| need it.
|
| I'm pretty sure about the battery payback, because I have
| a few years of per second consumption data in clickhouse
| and (very conservatively) simulated the battery. A few
| years ago any business case on storage was completely
| impossible, and now suddenly we're here.
|
| I could totally see this happen for the US as prices
| improve further, even if it's not feasible today.
| hvb2 wrote:
| Having done 2 solar installs, one over 10 years and one 6
| years, both going strong. Nothing else needed, it just sits
| there and produces.
|
| So, from my experience, that's not the case. Maybe the people
| you know keep tweaking because they're enthusiasts like you
| have with cars.
| vasco wrote:
| It could be as simple as a different model. In one of those
| it was easy to make it feasible if you had no cap on how
| much to sell back, but it was limited to consumption plus
| like 10% or something like that. Since the property used
| very little energy but had a big roof we thought itd be a
| good thing to produce green energy while making a little
| money or even just breaking even, but to break even we'd
| have to use way more energy which was completely against
| the original objective. So its not like the technology
| isn't able to do it but the rules can make it very hard and
| a few years less of operation for some components make the
| math very difficult if you're conservative and want to
| ensure break even within some reasonable timeline
| adgjlsfhk1 wrote:
| sounds like you were just doing the math for too much
| capacity. there's no rule that you have to cover your
| roof
| vasco wrote:
| Too little capacity and it takes 50 years to absorb the
| fixed costs.
| order-matters wrote:
| im a systems engineer and cost analyst who has put together
| some modeling myself as well. as a personal investment on
| your house, i agree. The economic value of solar seems to be
| best applied as neighborhood or block purchases, like as part
| of a co-op or hoa. they would need dedicated infrastructure
| like a communal parking lot with solar overhead, or running
| them on the property line borders with an easement underneath
| for servicing, using property fencing as main support (with
| upgraded fencing)
|
| basically, the way it really makes sense (to me) is to
| integrate it as part of a micro-grid system, possibly with
| generator backups and everything to also keep the lights on
| in the entire neighborhood if the main grid goes down.
|
| its a higher upfront cost on paper, but way less variables
| with the roof and you are grouping multiple peoples needs
| together so the gamble goes down on repairs. the poles for
| ground-mounting can be used for 40 - 60 years, so you would
| get multiple panels out of them
|
| probably a bureaucratic nightmare though
| RussianCow wrote:
| This is also true of heating and cooling, and I've never
| understood why we (in the US) build relatively dense
| housing communities but don't implement things like this.
| Having a separate air conditioner for each home, especially
| in a condominium/townhouse complex, has never made sense to
| me as it's so inefficient compared to central
| heating/cooling.
| systemtest wrote:
| -
| thescriptkiddie wrote:
| battery life span is defined as when the reach 80% of their
| original capacity. it's possible that the decline will
| accelerate after that point but they aren't suddenly useless
| IAmBroom wrote:
| Presumably an exponential decay, as for most tool
| lifetimes.
| toomuchtodo wrote:
| https://electrek.co/2026/01/06/catl-ev-batteries-
| significant...
|
| > For example, CATL is one of four LFP battery suppliers at
| the Zhangbei National Wind-Solar-Storage Demonstration
| Project in China. CATL's batteries are the only ones that
| have never been replaced, retaining over 90% of residual
| capacity after 14 years.
|
| Batteries are not only not worthless after almost 15 years in
| service, they still have sufficient capacity to continue to
| operate. If you need that capacity back lost to degradation,
| add a battery ~15 years from now, they will only continue to
| get cheaper.
| n8m8 wrote:
| Is an ETF simple?
|
| I get your point that in modern society, you can invest in an
| ETF in a few clicks, but in a way, owning your own
| infrastructure is simpler. Transform the sun into energy
| reserves with parts you can buy, understand, and install
| yourself from wholesalers.
|
| A power company is opaque, carries overhead, and requires
| complexity to serve at an institutional level. ETFs have a
| similar complexity/abstraction to their customers.
| hvb2 wrote:
| > Large solar farms and neighbourhood batteries operate at a
| much higher efficiency than domestic installations.
|
| Maybe, but that power is typically generated far from where
| it's consumed and so you have significant transmission
| losses.
| pjc50 wrote:
| Rather like the car, think of panels as buying 20+ years of
| electricity upfront rather than being exposed to market
| rates. You can buy a car upfront, on credit, lease it, or
| rent it; in all of those the longer you commit the cheaper it
| is.
|
| Not for everyone, but definitely for homeowners with suitable
| roofs and local utilities.
| SoftTalker wrote:
| I'm with you. I have no interest in owning, running, and
| maintaining my own personal electrical utility.
|
| I'm happy to pay monthly to let my electrical provider handle
| all that, and I'll invest my money in something with a better
| return.
| alberth wrote:
| Wont you need to replace the batteries around Year 10 and then
| this becomes a wash?
| boplicity wrote:
| Why would you need to replace the batteries? Do they fail
| outright at around 10 years, become unsafe, or do they just
| lose capacity?
|
| Curious!
|
| Even if they're at 50% capacity, they would still work,
| right? But if there are other considerations, especially
| safety ones, then that would definitely be a consideration.
| I'm not sure where to learn about this type of thing.
| mbesto wrote:
| > Do they fail outright at around 10 years, become unsafe,
| or do they just lose capacity?
|
| LiFePO4 generally degrades to 80% capacity after 10 years,
| that's it. Safety isn't an issue.
| lostapathy wrote:
| At which point if you're short on capacity (but who knows
| how your demand might shift over a decade) it's not like
| you need to replace the original batteries to get that
| 20% back, you will probably be able to just expand the
| pack to bring the capacity up.
| HexPhantom wrote:
| The payback math almost certainly improves if electricity
| prices keep rising faster than inflation
| nasmorn wrote:
| So what I take away is that he is using approx 3x electricity,
| that I do and that is including my electric car. I use an
| additional 5-7MWh of heat but on a heat pump that would still
| only be a max of 2MWh which doesn't even bring me to half of his
| usage, for a family of 4.
| j45 wrote:
| Interesting breakdown for the UK where sunshine isn't always
| plenty. If you have more sun this will be different.
|
| Solar tracking trees seem to be an interesting way to get
| wintertime solar way up.
|
| https://youtu.be/r7HwQdssbas
| mbesto wrote:
| It's wild how overpriced Tesla Powerwalls are.
|
| 16 kWh battery with all of the UL supported listings etc = $3300
| [0]
|
| 13.5 kWh Tesla Powerwall is $12k~$15k
|
| You would get your return way back quicker.
|
| [0] - https://www.ruixubattery.com/product-
| page/lithi2-16-battery-...
|
| EDIT: As others have pointed out, powerwalls have inverters built
| in so it's not totally apples to apples. You can get a beefy
| inverter for $5k and it's still cheaper and you wouldn't need an
| additional inverter every time you add a battery.
| toomuchtodo wrote:
| They have a 30% gross margin, they're just soaking up the
| federal US tax credit (which is also 30% for battery storage
| and extends through 2032).
|
| Alternatives: https://electrek.co/2025/12/28/opinion-its-time-
| to-start-rec...
| latchkey wrote:
| A few of the alternatives have been reviewed by Will Prowse
| as well. His YT is a treasure of information.
| https://www.youtube.com/@WillProwse
| dns_snek wrote:
| You're comparing the cost of a battery with a full system. That
| 16 kWh battery requires a ~$3000 inverter to go along with it.
| scarecrowbob wrote:
| Well, the math still maths, right?
|
| I am writing this off grid, using about 15kwh of batteries
| and a $1200 (6kw) inverter. My entire system puls panels and
| racking those panels, plus wiring some un-powered shacks was
| about $10k, though I did the work myself (which would
| probably hae been another 3-5k if I could have found someone
| to do it.
| thechao wrote:
| > which would probably hae been another 3-5k if I could
| have found someone to do it.
|
| Yo. If you can find an electrician to stop by my house and
| turn a light switch off for less than 1000$, please inform
| me. I got a quote for 25k$ to install a system that size,
| and that price. City code has me by the balls: I can't
| modify my main panel without inspection, the inspector
| won't show up without a licensed electrician, and
| electrician wants the labor. I pointed out that we're
| talking 8 hours of labor -- call it 2500$, lawyer money --
| and he was like "what's your choice". I'm in _Texas_.
| ozim wrote:
| For 2500$ maybe you can pass the exam to become licensed
| yourself. Like do it over the weekends.
| lostapathy wrote:
| This right here - I have been investigating getting my
| own contractor license for DIY work on a property I own
| that must be permitted but city will only issue permits
| to licensed contractors. Took a practice test for the
| exam on a whim and nearly passed it without studying.
| Anybody seriously considering DIY'ing the install of
| something like this probably could get a license without
| a lot of work.
| adrianmonk wrote:
| To get a journeyman electrician license in Texas, you
| need to have 8000 hours of documented on-the-job
| experience working under a licensed electrician[1].
|
| So you'd need to find an electrician who will let for you
| work them on the weekends, and if you work 8 hours every
| Saturday and every Sunday, then it will take you 500
| weekends.
|
| A residential wireman license only requires 4000
| hours[2], but I'm not sure if that kind of license would
| be good enough for the inspection.
|
| ---
|
| [1] https://www.tdlr.texas.gov/electricians/apply/individ
| uals/jo...
|
| [2] https://www.tdlr.texas.gov/electricians/apply/individ
| uals/wi...
| chasd00 wrote:
| "licensed electrician" is also timewalled behind a
| lengthy apprenticeship.
|
| From google's llm "..requiring 8,000 hours of on-the-job
| training (OJT) under a Master Electrician .."
|
| so even if you could pass the test you still don't get to
| become licensed until you've paid your dues in terms of
| time.
| ozim wrote:
| Isn't there an exclusion or lower entry requirement if
| you have a technical education like engineering degree?
| Like if not electrical engineering because I guess that
| would be obvious there should be lower entry bar - but
| for all others at least somewhat related...
|
| I guess if you want to dabble with installing battery
| packs with inverters, that's not your typical bachelor of
| arts who is trying to do so.
| scarecrowbob wrote:
| I mean, my MA is in Rhetoric... but hey.
|
| Where I am at (rural CO), as long as it can be inspected
| and meets code, the county is fine- you don't need a
| blessing. Septic is different (that's a $175 certificate,
| though). But for electrical all you have to do is meet
| codes, which isn't really super hard.
| lotsofpulp wrote:
| Run for political office espousing Texas' famous
| "freedom" that does not allow you to modify your own
| home.
| thechao wrote:
| "Freedom for me, rules for thee". Texas has always been a
| cesspit of political kickback. I mean ... not Illinois or
| New Jersey, but annoying enough.
| ozim wrote:
| From what I quickly checked you can modify your own home
| there is an exclusion for doing electrical work on your
| property - seems like main panel would be somehow
| excluded from what qualifies as "yours".
| tzs wrote:
| That exemption is from the state code and applies to
| "work not specifically regulated by a municipal ordinance
| that is performed in or on a dwelling by a person who
| owns and resides in the dwelling".
|
| They said it was city code causing their problem.
| fullstop wrote:
| 2019 prices, but it was $487 to move a receptacle from
| under a window to the left of the window prior to making
| that window opening a french door.
|
| In 2025 it was $1,100 to have an EVSE put in, including
| permit fees.
|
| I'm in Pennsylvania.
|
| Working with my township to get a permit / inspection was
| horrible -- they dragged their feet for months!
|
| I have to believe that I am one of a few people in my
| township who have done this the "right way".
| IAmBroom wrote:
| Weird. I'm in PA, and my electrician quoted me a flat fee
| of $100 for replacing my outlets with GFCIs (each).
| fullstop wrote:
| This wasn't replacing outlets, I do those myself. This
| was moving a receptacle four feet to the left and doing
| it through a finished basement.
| scarecrowbob wrote:
| Hoss I am sorry to hear that- I have literally no idea
| what electrical costs, as I've been doing it myself. If
| you're living close enough to other humans that the can
| observe and complain, then we're not really in the same
| situation.
|
| But that doesn't really change my point, does it? Like,
| if they are installing $6k worth of equipment and
| materials, then that's what the up-thread points was
| about paying 10K more for tesla-branded equipment, right?
| I get that at a certain point the labor makes the cost of
| materials less of a deal, but my point was that my
| battery+inverter+panels+material is still less than the
| equipment they are describing.
| mbesto wrote:
| That's fair.
|
| Better comparison:
|
| Author's config:
|
| 3x Powerwalls + inverters = 40 kWh
|
| 4.2 kW array
|
| PS39,360 = $53k USD
|
| Alternative:
|
| EG4 18kPV Hybrid Inverter = $5000
|
| 3x RIUXU = $9600
|
| 10x Trina Solar 435w panels = $1580
|
| Cabling, installations, etc. = $5000
|
| Total = $21k
|
| It's not even close...
| pchew wrote:
| This is still not an accurate comparison. I'm not a Tesla
| fanboy but of all of the major players in the non-diy game
| (Enphase, Franklin, Tesla, Sol-Ark) they provide the best
| value for money, and are impressive pieces of equipment.
|
| The EG4 18k has 11.5 kw backfeed capability, with a rather
| pathetic 65ish amp in-rush. Obviously 18kw usable solar
| capacity(they technically let you land up to 21kw, but only
| 18 is usable).
|
| The Powerwall system you outlined can take 60kw of usable
| solar input, has 34kw standing backfeed capability, and a
| whopping 555 amp in-rush (not a typo, it's 185 amps per
| unit).
|
| Not to get in to warranties, etc.
| mbesto wrote:
| None of those things matter when your solar array is 4.5
| kW and you have a standard 150A/200A grid in....
|
| Like I said, they basically are not sold to scale like a
| normal household uses electricity.
|
| EDIT: What the heck is in-rush and backfeed? Are you
| talking about AC input to charge the batteries? The 18k
| is 50A @ 240VAC (12kW) fyi. Also, why does the charge
| rate even matter there? For the AC output its also 12
| kW...the family is average 48 kWh days, which is 2 kW
| hourly average...
| labcomputer wrote:
| Inrush is surge capacity. Starting a big motor like an
| air conditioner can require 2x or 3x the continuous
| running amps, but only for a few seconds.
| pchew wrote:
| Inrush is exactly what it says it is, it's inrush
| current. When you have a sudden surge on something,
| that's inrush. Lots of appliances in your home have a
| large inrush, much larger than the breaker they're on.
| Inrush happens faster than a breaker trips, which doesn't
| matter when you're on the grid and the inrush is lower
| than your mainbreaker, it matters when you have an
| inverter in the way with a passthrough limit and an
| inrush limit. Typical central HVAC units have LRA over
| 100 amps.
|
| If we're talking about 'doesn't even matter with a 4kw
| array' well, hell, how the hell you gonna charge ~40kwh
| of battery with solar array that nominally produces 20kwh
| a day on its best day, assuming all conditions are
| perfect?
|
| Backfeed is what the inverter can push out from the
| battery to the home. It's the size of the tube coming
| from the gallons of water reservoir. EG4 18k has a tiny
| tube, no matter how much battery you put on it. Like
| emptying a 50 gallon drum with a drinking straw(and with
| the 4kw array, filling it with a 12 oz cup).
| mbesto wrote:
| > Inrush is exactly what it says it is, it's inrush
| current
|
| These are not terms commonly used in the industry, thanks
| for the clarification.
|
| > Lots of appliances in your home have a large inrush,
| much larger than the breaker they're on.
|
| And inverters are designed to compensate for short term
| surges too fyi. The 18k provides 65A for a few seconds as
| an example.
|
| > well, hell, how the hell you gonna charge ~40kwh of
| battery with solar array that nominally produces 20kwh a
| day on its best day, assuming all conditions are perfect?
|
| Because you can't and don't need to...you should be
| asking the author of the original post, because they do
| what pretty much every other grid tied system which is
| that you pass through the power from the grid.
|
| > Backfeed is what the inverter can push out from the
| battery to the home.
|
| https://www.wartsila.com/encyclopedia/term/backfeeding
| huh?
|
| > It's the size of the tube coming from the gallons of
| water reservoir. EG4 18k has a tiny tube, no matter how
| much battery you put on it.
|
| 1. The 18k can push 50A on each leg and most residential
| are sized at 150a or 200A, which are ridiculously
| oversized, so at most, even with two EVs and a 4 ton AC
| running in Texas, I max out at 150A. I can put 3 18k's in
| parallel if I really want to and its STILL cheaper than a
| powerwall battery/inverter combo.
|
| 2. There is no reason to have a "pipe" so large that it
| only is used for less than 5% of the overall runtime.
| This is why the powerwall setup doesnt make any sense.
| pchew wrote:
| >These are not terms commonly used in the industry,
| thanks for the clarification.
|
| It's such an industry term that it's literally a feature
| on multimeters.
|
| >The 18k provides 65A for a few seconds as an example.
|
| Yes, you'll see I gave you that spec in the opening
| comment. It's not a good spec for a whole home hybrid
| inverter.
|
| >the 18k can push 50A on each leg and most residential
| are sized at 150a or 200A
|
| That's not how you read a spec sheet for 240v device. A
| home service is 200 amp, at 240v. That's 48kw potential.
| 12k is 12k regardless of whether that's (120 * 50) + (120
| * 50) or 240 * 50. The legs aren't cumulative.
|
| (50a * 120v) + (50a * 120v) = 12kw
|
| A small home with a smaller 150 amp service is (150a *
| 240v), 36kw.
| ortusdux wrote:
| IIRC, the original idea was that they would pull older
| batteries from circulation when their capacities dipped, and
| then repurpose them as powerwalls, an application where weight
| is irrelevant.
|
| This was back when they expected the batteries to plateau at
| ~80% capacity after a few years, and they had battery swapping
| on the roadmap, so they needed to plan for a future where they
| had a steady supply of batteries that car customers did not
| want.
|
| The idea took hold, but the batteries lasted longer and
| swapping didn't pan out, so now they are competing with
| themselves for battery supply.
| benoliver999 wrote:
| Electric car battery degradation has been super interesting,
| in that they are going way further than people thought they
| might. Jonny Smith on youtube bought a 300k+ mile Tesla and
| the battery is at like 75% health.
|
| As far as I can tell if your battery isn't air cooled, it can
| go a very long way
| magicalhippo wrote:
| There was some research[1] that strongly suggested that
| varied use makes them last much longer than the steady use
| that most battery tests do. That is, bursts of high-current
| draw followed by moderate draw etc vs the constant current
| load typically used when evaluating battery performance.
| From the paper:
|
| _Specifically, for the same average current and voltage
| window, varying the dynamic discharge profile led to an
| increase of up to 38% in equivalent full cycles at end of
| life._
|
| This was unexpected, hence explains why they fared better
| than predicted.
|
| [1]: https://www.nature.com/articles/s41560-024-01675-8
| _Dynamic cycling enhances battery lifetime_ (open access)
| LordDragonfang wrote:
| Huh, unexpected is right. Bursts of heavy usage being
| better for longevity than steady usage goes against
| pretty much all conventional engineering wisdom.
| abdullahkhalids wrote:
| Without knowing anything about it, I would posit that
| degradation accelerates the longer the battery is kept
| above some threshold temperature.
|
| So, a heavy-burst+low results in a sudden high
| temperature then settling into a lower temperature.
| Steady flow keeps it at moderate temperature (above
| threshold) for a long time.
| magicalhippo wrote:
| The paper notes there are multiple degradation mechanisms
| at play, and they are influenced by different factors,
| such as age, cycles, depth of discharge, state of charge
| at rest and so on. Hence the non-trivial response to more
| realistic discharge curves.
|
| However they also note more material studies are needed
| to understand these mechanisms better.
| 1980phipsi wrote:
| Any idea why swapping didn't pan out for Tesla? My
| understanding is they are doing that in China.
| barbazoo wrote:
| Probably because the economics just don't make sense here.
| You'd have to have so many compatible cars on the road,
| driving all day with no opportunity to charge. I'm having a
| hard time imagining a place I've been to in North America
| where that'd seem logical.
|
| > they are doing that in China
|
| Are they actually doing that at scale?
| fartfeatures wrote:
| A little out of date now but:
|
| > As of June 2024, Nio had installed 2,432 power swap
| stations in China, including 804 along highways,
| representing the largest battery swapping network in the
| country. Nio aims to expand to 4,000 stations globally by
| 2025. By February 2025, Nio had 3,106 battery swap
| stations in China, with 964 located along highways. In
| January 2025 alone, Nio added 111 swap stations and
| provided 2,949,969 battery swap services, averaging
| 95,160 daily.
|
| https://enertherm-engineering.com/chinas-battery-swap-
| revolu...
| fennecbutt wrote:
| From the country that brought you mass wastage of
| bicycles, now we get battery swapping.
|
| This is pretty much just a "gamble by deploying as
| quickly as possible making our system the standard if it
| catches on" type of investment.
| Veserv wrote:
| What do you mean? It did pan out for Tesla. Faking a single
| demo granted them 75% more ZEV emissions credit government
| subsidys [1]. That increased their profits by hundreds of
| millions of dollars.
|
| All they had to do was go on stage and "swap" a battery
| without any clear video of the process and never
| "demonstrate" it ever again.
|
| This is a company known for faking prominent demos like the
| FSD demo (where it crashed into a wall during filming), the
| solar roof demo (where they used regular roof tiles and
| claimed they were solar panels), the optimus demo (where
| they were teleoperated), etc.
|
| Assuming they even did a battery swap, for which the
| official demo presents no clear video evidence, preferring
| overhead views over a close-up of the process or a glass
| enclosure to see the inner workings, it was at best a one-
| off custom-made device at the time. The one battery-swap
| station they claim existed has zero stories of any actual
| battery swaps, instead only evidence of it operating as a
| regular Supercharger [2].
|
| [1] https://thewaroncars.org/episode-88-tesla-is-a-fraud-
| with-ed...
|
| [2] https://slate.com/technology/2022/05/elon-musk-tesla-
| twitter...
| secabeen wrote:
| Battery swap was and remains really risky for anyone
| doing it. You're taking a $10k asset, and swapping it for
| another $10k asset of unknown provenance. Does anyone
| really want to be in a situation where they purchase a
| new Tesla with a brand new, max-range battery pack, then
| swap it once on a road trip and get one that's been used
| for 300k miles and is at 75% of original capacity?
| shawabawa3 wrote:
| As long as you can always swap your battery again I don't
| see the problem
|
| As long as the average battery health in the system is
| like 90% and the minimum is say 80% why would you care if
| you're getting a new battery every few days?
|
| If anything it removes a big cause of depreciation from
| your car
| bluGill wrote:
| That is fine if you always are swapping. However if you
| normally charge at home that becomes a big deal - if your
| current battery wears out/fails because it has 500,000k
| miles on it are you out a new one? Do you pay for the tow
| to get to a swap station? Again, if everyone always
| swapped this would be easy to amortize and not a problem
| but the mixed use.
|
| Of course this isn't a new problem. I know people who own
| their own welding gas tank - but they always swap the
| tank out. The place they swap at somehow handles when the
| tank needs to be re-certified - and people don't ask
| questions.
| bluGill wrote:
| The bigger risk is you need a standard battery pack. Sure
| you can put 3 in a truck or something, but you lose all
| the space that a standard battery size wouldn't fit but
| you can cram a cell in. Electric car design is about
| stuffing batteries where there is space - you need a lot
| of cells, but the individual cells are small.
| intrasight wrote:
| > of unknown provenance
|
| I don't understand the comment. Of course they know where
| the batteries come from. They know everything about the
| battery.
| labcomputer wrote:
| They didn't fake the demo, but the legislature quickly
| rewrote the law because it was intended to give Toyota
| ZEV credits for hydrogen cars.
|
| Tesla did briefly operate a swap station at the site of
| the Harris Ranch Supercharger until California changed
| the rules.
|
| There are several reports from people who used it on
| teslamotorsclub.com, and I saw it with my own eyes.
|
| Hilarious that your source is Ed Neidermeyer. Perhaps the
| only thing more impressive than Elon's lies about the
| state of self driving are Ed's lies about how Tesla is
| going bankrupt Any Day Now.
|
| It's ok though, Ed's stock manipulation antics enabled me
| to stuff my IRA with Tesla shares (since sold, when Elon
| went nuts) and make a nice little headway on my
| retirement savings.
| Veserv wrote:
| Cool. Then if you are not lying, then it should be easy
| to present a clear video demonstrating the automatic
| battery swapping machine in action and swapping out a
| battery in 90 seconds as claimed in the demo.
| labcomputer wrote:
| > Any idea why swapping didn't pan out for Tesla?
|
| ~~Two~~ Three things:
|
| 1. California changed the rules shortly after Tesla
| demonstrated their swap station, which practically
| eliminated the tax credit for battery swap (at the behest
| of lobbyists for Toyota, who were backing Hydrogen Fuel
| Cell technology). Specifically, the credit would be
| prorated by the percent of "fast refueling" sessions a car
| did, so EVs primarily charged at home received almost
| nothing while HFCV got the full credit. Building swap
| capability adds complexity to the car (think about all the
| fluid connections), which isn't worth it without credits.
|
| 2. It was also around this time that a Model S ran over an
| anvil (or something) which punctured the pack and started a
| fire. In response, Tesla added an aluminum battery shield,
| which further complexifies swapping and was probably the
| final nail in the coffin.
|
| 3. The logistics of storing your very expensive battery (so
| you could get it back later) basically make the system
| unworkable. When the Tesla swap station at Harris Ranch
| (you can still see the former building, next to Harris BBQ,
| which currently houses the restrooms) was operational, you
| had to make a reservation some hours in advance so that
| Tesla could have a pack ready and be ready to take your
| pack to/from storage.
|
| 3a. Gresham's Law. Without eventually returning the pack to
| the original owner, there is an adverse selection problem:
| people with very weak packs will gladly roll the dice on a
| swap, but those with brand new packs are reluctant. So the
| average quality of packs in the swap network will quickly
| decline creating a death spiral.
|
| 3b. You could probably fix 3a by leasing the battery (or
| selling battery-as-a-service) but car buyers mostly don't
| like that, especially back in 2013.
| phantom784 wrote:
| I could potentially see value in a car with a smaller
| built-in battery for use around town, and an empty space
| for a larger battery, that you rent from swap stations
| for longer road trips. Of course, that doesn't work with
| anything on the road today.
| O5vYtytb wrote:
| That's not really apples-to-apples comparison. The Tesla
| batteries are AC coupled so they work with an (AC coupled)
| microinverter array. For a DC coupled battery you have to have
| a hybrid inverter and DC couple the batteries.
|
| Your point that they are overpriced still stands though.
| mbesto wrote:
| Ya as someone else pointed out, powerwalls essentially have
| an inverter built in. But this is really dumb to have
| inverters tied directly to each powerwall battery. This is
| like anti-scale.
| HexPhantom wrote:
| I think "overpriced" depends a lot on what problem you're
| trying to solve
| mbesto wrote:
| Powerwalls don't uniquely solve any problems other brands
| can't do.
| IAmBroom wrote:
| A statement so vague as to be tautologically true.
| jillesvangurp wrote:
| There's going to be a bloodbath in that market in the next
| years. There are a lot of battery producers and most of them
| are not producing at full capacity. At the same time,
| manufacturing cost is dropping as well.
|
| Some battery makers are producing batteries at a cost level of
| around 60$ per kwh. At that cost, the 16kwh battery would come
| out below 1000$ (not the same obviously as the product price).
| Sodium ion might push those prices even lower. Below 50$
| soonish and eventually closer to the 10-20$ range in maybe 5-10
| years. At that point we're talking a few hundred dollars for a
| decent size domestic battery. You still need packaging,
| inverters, etc. of course.
|
| But the ROI at anything close to those price levels is going to
| be pretty rapid. And it wouldn't break the bank for households
| across the world. Add a few kw of solar on roofs, balconies,
| etc. It won't solve everyone's problems and certainly not in
| every season. But it can help reduce energy bills in a
| meaningful enough way. Even in winter.
|
| Also worth pointing out: most of the US is south of Cornwall.
| The Canadian border runs roughly at 49 degrees latitude.
| Cornwall is the most southern point in the UK sits at 50
| degrees. If it can work there, most of the US has no excuse.
| Also, the UK isn't exactly well known for their clear blue
| skies. Even people in Scotland much further north manage to get
| positive ROIs out of their solar setups.
| itsamario wrote:
| Companies like Schneider electric have systems for 25-50% the
| hyped brands but they don't provide batteries.
|
| This is the company that owns APC so its not like theyre new
| or untested. They just don't bother with brand awareness
| nagisa wrote:
| Its weird to read about Schneider Electric not bothering
| with brand awareness. They aren't a household brand, sure,
| but they are well up there with Siemens and the like in
| industrial/b2b sector and their marketing budget is
| allocated accordingly.
| MisterTea wrote:
| All they did was buy up everyone's else brand and put
| their brand over it. Modicon PLC's, Magnecraft relays,
| etc.
| raddan wrote:
| I installed a 16.5kWp ground-mount array a month ago. I live
| in the US Northeast, in a mountainous location that means we
| get late sunrises and early sunsets. Nevertheless, based on
| my one month of data, it looks like we can generate all the
| power we need for our household on a sunny winter day,
| excluding electric vehicles. Even on overcast days, we can
| sometimes offset a significant portion of our usage. My
| locale does not have time-of-use rates, so there's no point
| trying to do arbitrage for electricity prices. So right now I
| just have our battery configured for backup. My hope is that
| during the summer months I can reconfigure the system to use
| the battery to reduce grid reliance instead.
|
| The expiring tax credits were what forced my hand. I'm the
| kind of person who likes to install things himself, and I
| probably would have gone that route for solar too, because
| the materials costs (sans battery) aren't even half of the
| total cost.
| torginus wrote:
| Here in Europe, we got more than a month's worth of foggy,
| cloudy weather (something that looks like will keep being a
| thing), which is something I became painfully aware of as
| an owner of a solar setup.
|
| No amount of battery banks can tide over such a long
| stretch.
|
| By the way, let me ask you - considering your location, you
| must be getting a lot of snow, how do you deal with it, is
| it a problem? Panels are quite hard to reach on the roof.
| yomismoaqui wrote:
| Where in Europe? Between Spain and Denmark there is a lot
| of variance in temperature, sun and rain...
|
| Talking about the weather "in Europe" is like talking
| about the shoe size a family of 10 wears.
| raddan wrote:
| I do indeed get a lot of snow. In January and February it
| snows roughly once every two days, although usually in
| small amounts.
|
| Fortunately I have a ground mount. The bottom row is
| roughly at waist height. I can (and have been) sweeping
| the panels off with a large push broom. Because my array
| is so large, I can only reach the bottom half of the
| array. But this usually is enough. When the panel starts
| to generate power, it also tends to heat up; the snow on
| the top half then often slides off on its own.
|
| I might invest in a longer broom. It is not uncommon for
| people here to own "snow rakes" to remove large snow
| loads from their roofs. These usually have a rubberized
| "rake" with a very long aluminum handle. Or the novelty
| of this might wear off and I'll just let the panel do its
| own thing. It is pitched rather steeply (close to 45deg)
| and based on my observations of my neighbors, panels tend
| to shed the snow on their own eventually.
| Aurornis wrote:
| I'm not so sure. There are a lot of large-scale applications
| that would gobble up battery supply if it hit a certain price
| point. Grid-scale storage and datacenters, for example.
|
| If prices for residential gear falls too much, I expect the
| manufacturers would just stop making it and focus on the
| commercial options instead.
| greycol wrote:
| One thing to remember is as it becomes more widespread line
| costs will go up (assuming they are subsidized by kwh use,
| which they generally are) and no-sun power prices will
| increase as it's the only time when the grid needs power from
| non solar producers and they still need to cover cost
| incurred while they're not producing.
|
| That will push the economics towards completely off grid
| systems as more people adopt solar, so if people are planning
| it for themselves they should probably consider that it will
| make sense to expand their set up in the future and that
| there might be a price crunch due to higher demand because of
| larger systems coupled with more people wanting to switch.
| port11 wrote:
| My partner works in the field and we once talked about
| this. I think the idea is that individual consumers' and
| businesses' batteries can serve the grid as needed. For
| example, if your car is fully charged and you don't need it
| today, it can top up local needs.
|
| So I think the writing isn't on the wall yet for line price
| going up, although I'm of course talking of a) Belgium, and
| b) a future that could go wrong if utilities don't fund
| smart metering.
| ViewTrick1002 wrote:
| An interesting possible is the grid becoming smaller.
| Neighborhood scale.
|
| In many places from Central Europe and further north
| dealing with arctic cold spells and dunkelflautes are near
| impossible for a home solar and storage setup.
|
| But you also don't want to pay for a continental scale grid
| the remaining 51 weeks.
|
| So in your neighborhood add some wind power and a good old
| trusty diesel/gas turbine running on carbon neutral fuel
| and keep the costs to a minimum.
| torginus wrote:
| Majority of the world's battery manufacturing capacity is
| dominated by just a small handful of players:
|
| https://en.wikipedia.org/wiki/List_of_electric_vehicle_batte.
| ..
|
| Just 11 companies control 90+% of manufacturing capacity, I
| think they might need to adjust their ambitions in the face
| of demand, but I think most of them are too big to fail.
| nop_slide wrote:
| You might find https://www.basepowercompany.com/ interesting,
| 25kwh battery for $700 down and $20/month
| modeless wrote:
| The crazy thing is you can buy a 69 kWh battery from Tesla for
| $36,990, and it comes with a whole car too.
| microdrum wrote:
| For what it's worth, Tesla PV/batt inverters are bad, almost as
| bad as the Chinese manufacturers mentioned ITT. PW3 has very
| high failure rate ~10%+RMA, not good enough IMO to be in the
| path of power at my house.
|
| (Their motor inverters are world-class, but totally different
| topology)
| torginus wrote:
| A small thing I want to remark is that at that price, a Model 3
| costs less than 3x, and has more than 3x the battery capacity.
|
| Considering DC connectors on EVs provide a direct electrical
| connection to the battery terminal, and the charge-discharge
| circuitry in residential hybrid solar inverters can handle them
| just fine (provided it supports the voltage ranges, but people
| did this).
|
| I think it's an enormous missed opportunity, that the most
| common charger standards don't support this (CCS2 doesn't,
| Chademo does, no idea about NACS)
|
| If this was a thing, I think it would completely reshuffle the
| EV market, I don't know how used residential batteries
| depreciate, but I doubt they lose more than half of their value
| in 5 years like EVS do.
| wang_li wrote:
| The Ioniq has the ability to provide battery power out so you
| can plug your house in.
| torginus wrote:
| I'm talking about something a bit different - the Ioniq
| uses a V2L, which means it has an onboard inverter that
| generates AC mains voltage through the plug, and can be
| used to provide equipment directly.
|
| What I'm describing is using the cars DC charge port and
| connecting it to inverters DC battery port.
| tzs wrote:
| It is interesting to compare to V2H systems.
|
| I believe Chevy offers V2H on all 2026 Equinox EVs. Enabling
| this needs their V2H Enablement Kit and I believe you also need
| their PowerShift Charger. That would be around $38k for a 2026
| Equinox EV LT, which has an 85 kWh battery, $6300 for the V2H
| Enablement Kit, $2000 for the PowerShift Charger. Installation
| via the company Chevy says to use is $2000-5000 according to
| the net.
|
| That brings us to $51-52k, and would give 70ish kWh of usable
| backup capacity. That's around $750/kWh of capacity.
|
| Getting that capacity with Powerwalls would require 5 of them
| and cost quite a bit more.
|
| Plus, with the V2H approach when you aren't having a power
| outage you can use it as a car. :-)
| chris222 wrote:
| Yah, check this one out.
|
| https://www.docanpower.com/panda-52v-942ah-48kwh-prebuilt-pa...
| mbesto wrote:
| I actually own three of 15 kWh versions :)
|
| They are cheap and they work but they're not UL listed...so
| they dont go anywhere near my home.
| KaiserPro wrote:
| Now they are overpriced but up until 2022/3 they were the best
| value unit.
| homebessguy wrote:
| In the UK, where the OP is from, the equivalent of the battery
| you linked is available from Fogstar for PS1850 (includes 20%
| VAT), shipped. Without the VAT that works out at ~$2000. A
| compatible high end 9kW inverter is available for around
| PS1200.
|
| The ROI is really attractive once you look past the overpriced
| kit.
| deadbabe wrote:
| Heat Pump water heater running in heat pump only mode is a way
| better ROI if you're looking to save some money on electricity.
| dlcarrier wrote:
| Where I am in California, there's a $30+/mo charge to connect to
| the grid, and the largest savings from a battery was being able
| to disconnect from the grid. There's lots of time I have excess
| power generation when I could give to the power grid, if I were
| connected, but I would have to pay extra to do so, so the
| potential goes unused.
| systemtest wrote:
| Is delivering back to the grid economical in California? Where
| I'm from people disconnect solar panels on sunny days because
| it costs them money to return to the grid.
| dymk wrote:
| PG&E does net metering, but even at a sub 1:1 rate past your
| net usage it does not make sense that it costs more to send
| energy back to the grid
| coryrc wrote:
| The worst that happens is you get paid back at the wholesale
| rate (from your bill, not live market price) instead of
| discounting kwh-per-kwh.
| systemtest wrote:
| But is that rate always positive? Where I'm from during
| peak sun hours, the rate is negative and you end up paying
| money to deliver money to the grid. They do this to
| incentivise you to decouple your solar installation during
| peak sun hours so the net doesn't get flooded with too much
| energy.
| Rebelgecko wrote:
| In CA it can be 0 but not negative.
|
| Depending on when you signed up for NEM you may have a
| guaranteed floor like 4C//kWh or even much more.
| coryrc wrote:
| Yes, you asked about California. I assume you are not in
| California.
| Aperocky wrote:
| Is the disconnect automatic? what happens when you're not
| connected to the grid but battery is full?
| systemtest wrote:
| This is for solar only installations. People are advised to
| flip the breaker of their solar installation when energy
| prices are negative as it would cost them money if they
| deliver electricity to the grid. This helps to reduce
| strain on the grid.
| rconti wrote:
| I'm on NEM2.0 so I can generate more than I use at peak hours
| and push into the grid for higher credit value than I consume
| overnight to charge my car.
|
| Still, I don't see the value proposition for batteries on
| NEM2.
|
| If I wasn't using _any_ electricity at my house, and I could
| 100% charge the batteries off-peak and push the power back to
| the grid at peak, I'd only be arbitraging like 5-10c/kWh *
| 15kWh per pack.
|
| So, $1.50 per day, per pack. Unless I'm totally thinking
| about this wrong. The spread between peak and off-peak rates
| is just too small.
| riku_iki wrote:
| It probably means that you would contribute less than cost of
| maintaining your grid connection ($30/mo)
| mikaeluman wrote:
| The reason is that California has made their grid extremely
| vulnerable. The grid already heavily overproduces solar so it
| is reasonable to have negative prices. There is no sink
| available.
| coryrc wrote:
| Unfortunately no urban places allow you to remove from the
| grid.
| domh wrote:
| > The batteries can fill up on the off-peak rate overnight at
| PS0.07/kWh, and then export it during the peak rate for
| PS0.15/kWh, meaning any excess solar production or battery
| capacity can be exported for a reasonable amount.
|
| Honestly I didn't know this was allowed.
|
| I recently got a heat pump and am on a time-of-use tariff
| (https://octopus.energy/smart/cosy-octopus/) and have been
| thinking about pulling the plug on battery storage for a similar
| purpose (charge during the cheap hours; run the house off battery
| during the day). I am currently using between 40-50kWh per day -
| anyone have similar usage to this and can recommend batteries for
| this?
| syncsynchalt wrote:
| It benefits the grid to have people consume extra power when
| there's an oversupply, store it and give it back when there's
| undersupply. Why shouldn't it be allowed (even encouraged)?
| coryrc wrote:
| Because of regulatory capture, only the big companies should
| be allowed to sell at retail and make profits.
| Perz1val wrote:
| Why wouldn't it be allowed? They're essentially renting their
| batteries and grids generally lack storage
| domh wrote:
| Yeah not sure really. I thought these time of use tariffs
| were intended for charging EVs and using heat pumps, not
| charging batteries and selling the energy straight back to
| them later on in the day. But when you put it like that
| (decentralised grid storage) I guess it makes sense.
| dabeeeenster wrote:
| I just had Solaredge battery installed in my house in the UK
| (Had a solaredge PV and inverter so made sense even tho it was
| more than other setups). If you are up for a challenge
| https://springfall2008.github.io/batpred/ is AMAZING and
| basically optimises when to charge and discharge your battery.
|
| I've got a heat pump and think my paypack period is going to be
| about 6 years.
|
| Hit me up on bluesky (in profile) if you want more info!
| domh wrote:
| Thanks! I will check out Solaredge. Biggest thing right now
| with the heat pumps is lack of consistency of software.
|
| Just looking at Havenwise (https://www.havenwise.co.uk/) and
| my manufacturer isn't supported.
| webjunkie wrote:
| A word of caution: It's worth factoring in battery
| depreciation. That 7p-15p arbitrage isn't "free" profit: you
| pay round-trip losses and you burn cycle life. If you assume
| ~PSX installed, ~Y usable kWh, ~Z cycles to 70-80% capacity,
| the wear cost alone is often several pence per kWh throughput,
| which can wipe out most of the spread.
| Scott_Helme_ wrote:
| The only restriction placed on you is the export rate, which is
| provided to you by the DNO here in the UK. We had a limit of
| 3.8kW placed, which is programmed in to the batteries by the
| installer.
|
| Octopus also have more flexible battery export tariffs if you
| want to explore those: https://octopus.energy/smart/flux/
| oklahomasports wrote:
| Aren't powerwalls overpriced?
| bstsb wrote:
| this can be disallowed in the UK, depending on their agreement
| either their provider. the OP is exporting way more energy than
| they have ever produced through solar; in effect they're selling
| back off-peak energy to the grid, which is making a profit
| drnick1 wrote:
| > Having our full costs returned in ~11 years is definitely
| something we're happy with
|
| Except that after 11 years the equipment will have broken down or
| become obsolete, at which point you have to start over.
|
| > we've also had protection against several power outages in our
| area along the way, which is a very nice bonus.
|
| This seems to be the real benefit of the setup.
| kccqzy wrote:
| What breaks in 11 years? Solar panels and batteries both last
| longer than that.
|
| As for your other point of becoming obsolete, why care about
| chasing latest fads for home appliances.
| Ensorceled wrote:
| Are you sure? Lots of people are telling me that batteries
| only last 4-5 years tops and solar panels usually burn out
| before 10 years /s
|
| I particularly love when they are telling me that my 11 year
| old Prius' batteries will only last 5 years before they are
| junk.
| ishtanbul wrote:
| This is totally wrong. I work in the industry. Solar panels
| should last for 30 years, but they degrade in capacity by
| 0.5 to 1% per year, depending on environmental conditions
| (temp, radiation, etc). Lithium batteries from tier 1
| suppliers can last at least a decade of regular use. It
| depends on how their cycling and state of charge is
| managed. If you keep them between 20% and 80% charge, they
| can last incredibly long.
| Ensorceled wrote:
| /s is the sarcasm tag.
| IndrekR wrote:
| > Except that after 11 years the equipment will have broken
| down or be obsolete, at which point you have to start over.
|
| If my calculations are correct, that setup probably lasts at
| least 30 years. This is not a cell phone battery and panels do
| not degrade that fast.
| bunderbunder wrote:
| The equipment doesn't have moving parts so I wouldn't expect it
| to break down so quickly.
|
| The real surprise for me was how much having solar panels on
| your roof adds to the cost of roofing work. Which is a problem
| because the roof is likely to need repairs more often than the
| solar panels.
| epistasis wrote:
| Yeah it's a tradeoff on the roof. The panels also increase
| the lifetime of the roof.
|
| Solar panels are incredibly durable, there's a thriving
| secondary market for used panels, and we're likely to see
| 30-50 years of usage out of any panel created today.
|
| Cracking the problem of making the roof _out of_ solar panels
| seems like a fantastic engineering challenge. But not one
| with small tiles, make the roof out of the bigger cheap large
| panels. I would love to see startups working on that. Asphalt
| roofs look like crap anyway, changing to shiny panels would
| be a huge improvement IMHO
| lysace wrote:
| Solar panel investment has slowed down substantially in Sweden.
| Basically, when the sun is shining, electricity is close to free.
| Similar situation with wind power.
|
| Neither technology can move forward until there's a 100x leap in
| electricity storage costs. Like a bunch of us said 10 years ago,
| because we remembered high school physics.
| pjc50 wrote:
| Sweden is also extremely far north, so seasonality is a
| problem. Good synergy with Norway, though.
| mikaeluman wrote:
| This is indeed nice for a well-to-do home. But there is a tragedy
| of the commons issue here.
|
| The grid needs to be up 24/7. And while peak usage is just that,
| the grid capacity still needs to support peak usage.
|
| This can theoretically be done using batteries but not for an
| extended amount of time. To say we can have batteries for 2 weeks
| of normal consumption is highly improbable.
|
| The metals do build those batteries do not exist. Or put in a
| worse way, the mines do not exist.
|
| An off the cuff calculation of costs and the massive amount of
| batteries required in the context of Sweden can be found (you
| need to translate) here:
| https://www.tn.se/naringsliv/40181/utrakning-60-globen-batte...
|
| In other words, 60 full scale Globen arenas of batteries to
| replace current Swedish nuclear production.
|
| So for small houses these investments can make sense currently.
| But from a larger perspective it's not that interesting.
| epistasis wrote:
| Residential solar with batteries greatly aids the grid and
| reduces costs for the entire system.
|
| > The metals do build those batteries do not exist. Or put in a
| worse way, the mines do not exist.
|
| Lithium and sodium, the two most promising battery metals, are
| not usually mined, though in Australia I hear there is mining.
| It's more of a brine process. All across the US, frackers are
| finding that all that water they are pulling out is a fairly
| rich lithium brine.
|
| The amount of metal needed for 2 weeks of batteries is pretty
| trivial compared to the system we've built for extracting
| fossil fuels, and iron, etc. The bigger demands for
| electrification are acutally copper! Gotta wire everything....
|
| Grid batteries on the GWh scale make a ton of sense financially
| and environmentally, and are revolutionizing the grid. Never
| before has the grid had a way to store electricity on a grand
| scale, which changes the entire nature of the beast. It's was
| one of the only massive systems we had where there wasn't
| buffering!
|
| With storage, we can alleviate congested transmission without
| super costly transmission upgrades. On exist lines, we can the
| usage massively, reducing costs, because now we can buffer
| across time to shave off the peak demand.
|
| Batteries are easy to build, environmentally friendly, and like
| a swiss army knife in their number of applications. We will be
| producing TWh of batteries a year in modern economies, and they
| last ~20 years, meaning that for the foreseeable economic
| growth in the coming decades, we'll easily have a peta-watthour
| of battery storage in use at a time.
| mikaeluman wrote:
| I don't agree. Lithium and Copper are mined and given
| electrification scenarios there is a projected supply
| deficit: https://www.iea.org/reports/global-critical-
| minerals-outlook...
|
| Those prices are outdated now since practically all metals
| are surging.
|
| There has indeed been great growth in battery capacity but
| it's as I said nowhere near able to supply a country like
| Sweden during the winter. It is off by orders of magnitude.
| We need 5TWh for that. It is not going to happen any time
| soon.
|
| I understand California is different. Still, one would need
| to do these risk scenario calculations. Have they been made?
|
| I know California has rotating blackouts already as it is. I
| really don't have any idea how people find that acceptable.
| If it happened in Sweden the government would be replaced on
| the day. It would be a real disaster.
|
| I will be a bigger believer if a state like California can
| actually show its possible.
|
| For sure I hope technology improves but the current ideas of
| solar+battery are simply highly unlikely.
| epistasis wrote:
| Your link does not support the idea of a supply deficit, at
| least that I see. Propel panicked about lithium under
| supply, prices surged and didn't even affect battery prices
| much, and now we are in oversuppply. The worst that can
| happen is lag time between demand increase and supply
| match, and there are substitutes for all key metals for
| most applications, even copper.
|
| Every country will have to figure out how to supply its own
| power, but Sweden's seasonal variation in renewable
| resources is not likely to be fixed by batteries, even
| though batteries will be abundant and in massive supply
| throughout the rest of the world. If Sweden can't figure
| out, or merely can't, take advantage of great cheap new
| technology, they will be at a disadvantage compared to
| countries that will
|
| > I know California has rotating blackouts already as it is
|
| You don't know that because it's not true. Due to planning
| not taking into account climate change, there were a few
| days with demand above expected ability to provide
| capacity, but there were no blackouts because people were
| asked to voluntarily cut back on excessive cooling. That
| mere ask was more than enough to get through the few days.
| And it was fixed the next year, by what? By batteries!
| Adding nuclear wouldn't have helped, but batteries were the
| perfect solution. Perhaps nuclear can help Sweden, but it
| will be far more expensive than the solutions available to
| other countries.
|
| It is quite funny that what I thought was US propaganda has
| been spread to Sweden for repetition. Even including the
| IEA report that doesn't say what people claim it says!
| Rebelgecko wrote:
| What gives you that impression? Unless you're looking at
| the pre-9/11 grid powered by Enron(tm), rolling blackouts
| aren't a big deal in California. I think since 2001 there
| was a single 2 day event limited to certain regions, I
| don't know anyone personally who lost electricity due to
| rolling blackouts.
|
| The CA grid has also scaled up battery storage surprisingly
| quickly. A few years ago it was in the single digit mWh,
| not really a meaningful fraction of the grid. Now it's
| measured in gigawatt-hours.
| ImPostingOnHN wrote:
| What makes you think I need batteries for 2 weeks of normal
| consumption?
| epistasis wrote:
| Nobody _needs_ that, but from my point of view batteries will
| be so cheap and abundant that we will likely get to having 2
| weeks of storage just sitting around the grid or rolling on
| wheels.
|
| People always underestimate where exponential cost decreases
| will take us. Current battery production grows by 10x in a
| mere 5 years. In a decade, the time it takes to build a
| nuclear power plant, we will grow our battery production by
| 100x. Not enough people take this seriously, or even know
| that the trend exists.
| mikaeluman wrote:
| We practically don't see the sun in northern Europe during
| winter. And yes, the wind might not blow either.
|
| I consider 2 weeks of supply a bare minimum.
| ImPostingOnHN wrote:
| How would 2 weeks of battery help you in that situation?
| The winter lasts a lot longer than 2 weeks. So after 2
| weeks of no sun, wouldn't you be just as screwed as if you
| had 1 week of battery storage?
| coryrc wrote:
| I don't see where anyone is proposing this as multiple-week
| storage for the whole grid?
|
| That's why you're investigating hydro storage:
|
| https://www.ess-news.com/2025/02/11/fortum-explores-new-pump...
| bob1029 wrote:
| The rooftop solar game in Texas is strongly into scam territory.
| Most homes I see with panels on the roof are _two story_ homes
| where you have a negligible amount of area to work with relative
| to interior space. There was a point where you 'd have to deal
| with a door-to-door salesman approximately every 48h for an
| entire summer.
|
| The most realistic residential installation I've seen was firmly
| on the ground at a ~2 acre property. The panels were much larger
| and heavier (i.e., capable) than what you'd typically find on a
| roof. It's much easier to build and maintain a solar array when
| you don't need a ladder/crane to move things around.
|
| I think that it's great that we want to participate in making
| things better, but not every situation makes sense. When you
| factor in all of the downstream consequences of sub-optimal, fly-
| by-night installs, it starts to look like a net negative on the
| environment. I'm not trying to claim that all rooftop solar
| projects are bad, but _most_ of the residential ones I 've seen
| make absolutely zero economic sense.
|
| Large scale wind and solar projects are the best way forward. You
| get so much more bang for buck. I'd consider investing in these
| projects or their upstream suppliers and owners if you want to
| get involved financially in making the environment a better
| place.
| HexPhantom wrote:
| I think you're mixing two very different things: the tech and
| the sales channel
| bob1029 wrote:
| I was hoping to illustrate that without a hyper-aggressive
| sales campaign not as many people would have gone along with
| a bad installation.
| toomuchtodo wrote:
| Find a solar coop if you can to avoid the sales pain. They
| will assemble a group of homeowners and bid the entire
| group install out to achieve cost efficiency. Ground
| installs are cheaper and easier, imho, whenever possible
| (but depends on land availability and favorable solar
| insolation).
|
| http://solarunitedneighbors.org/ |
| https://solarunitedneighbors.org/locations/
| megaman821 wrote:
| For homes, solar car ports and pergulas look attractive if you
| are land constrained. No holes in your roof, and it is Texas,
| so more shade is always appreciated.
| ishtanbul wrote:
| what is the scam exactly? Installing a small amount of solar
| isn't categorically worse than installing a lot of it. Its just
| smaller.
| testing22321 wrote:
| So people with these small installs are only saving $500 a year
| and not $1000?
|
| I'll take free $500 all day long please.
| HexPhantom wrote:
| This setup only really works because of a very specific
| combination of smart tariffs, EVs, and aggressive automation.
| Without those, the math would look very different
| Scott_Helme_ wrote:
| Absolutely -- tariff choice, storage, and automation make a
| huge difference.
|
| The article isn't claiming this setup is universally optimal,
| just showing what's possible when those pieces are combined and
| used deliberately.
| zackmorris wrote:
| I've been following a story where Elon Musk's xAI is building an
| 88 acre solar farm next to its Colossus data center near Memphis
| TN after public outrage due to running 35 methane gas turbines
| without a permit, which increased NOx emissions enough to
| allegedly impact health:
|
| https://techcrunch.com/2026/01/12/trumps-epa-plans-to-ignore...
| 88 acres = 356,124 m2 4.56 kWh/m2 per day solar insolation
| (4.5 is typical for much of the US) 4.56 kWh/m2 per day \*
| 356,124 m2 = 1,623,924 kWh/day = 67,664 kW = 67.66 MW average
| 1000 W/m2 \* 356,124 m2 = 356 MW peak
|
| They're estimating that they'll get 30 MW on average from that,
| but I'd estimate more like 15 MW at a solar panel efficiency just
| over 20%. Still, the total cost for that power should be less
| than for turbines, since solar is now the cheapest electricity
| other than hypothetical nuclear (assuming an ideal breeder or
| waste-consuming reactor and excluding mining/waste
| externalities/insurance).
|
| 30 MW is still only 10% of the the 300 MW used by the data
| center. But there's lots of land out there, so roughly 1000 acres
| per data center doesn't seem that extreme to me. That's a 4 km2
| or 1.5 mile2 lot, or about 2 km or 1.25 miles on a side.
|
| Basically every GPU server uses 1 kW (about 1 space heater),
| which puts into perspective just how much computing power is
| available at these data centers. Running a GPU continuously at
| home would need 24 kWh/day, so with > 20% efficiency panels
| that's 4.5*.2 = 0.9 kWh/m2 per day, so 26.67 m2, so at 2 m2 per
| commercial solar panel and assuming that my math is right: that's
| about 14 panels considering nights and seasons.
|
| It's interesting to think just how many panels it takes to run a
| GPU or space heater continuously, even when they put out 500 W or
| 250 W/m2 peak. And how cheap that electricity really is when it's
| sold for on the order of $0.15 per kWh, or $3.60 per day.
|
| I've found that the very best way to save on your electric bill
| is to have a few south-facing slider doors and windows, which is
| like running a space heater every square meter of window. There's
| just no way that any other form of power generation can compete
| with that. Also, I feel that we're doing it wrong with solar.
| This analysis shows just how much better alternatives like trough
| solar and concentrated solar (mirrors towards solar panels) might
| be cost-wise. On an ironic note, solar panels now cost less than
| windows by area, and probably mirrors.
| pier25 wrote:
| PS3,632.86/year for electricity seems wild. 17,000kWh/year is
| about 46kWH/day. We consume less than 3kWh/day on average.
| coryrc wrote:
| Do you have electric heat? Do you have automobiles and do you
| fuel them with electricity?
| pier25 wrote:
| We do use electric heating from time to time but it's not
| constant. No electric cars. Still a 15x increase seems huge.
|
| Increasing electricity production 10x to electrify cars is
| not going to be achievable soon. Either via the power grid or
| home solar panels. Most people cannot afford to invest $40k
| in solar panels, batteries, etc.
| coryrc wrote:
| Well, people who live somewhere where they need heating use
| more energy to stay alive than those who don't. Too bad
| California is so expensive because we could decarbonize the
| US significantly just by making it affordable for people to
| move there from Northern states.
| dlisboa wrote:
| It's crazy how power hungry UK homes are, or maybe it's UK power
| consumption habits in general.
|
| I use about ~300 kWh/month. A little bit more with AC some times
| of the year. What are you even powering with 15000 kWh?
| jjice wrote:
| Are you commenting on this article? This person is in the UK.
| You can see it on their domain, their calculations using
| pounds, and then mention living in the UK multiple times in the
| "Our setup section".
| bradphipps wrote:
| They explain in the article.
| GordonS wrote:
| The OP is a significant outlier - the UK average is around
| 7.4kWh/household/day[0], or 11.2kWh specifically for large
| households.
|
| [0] https://www.britishgas.co.uk/energy/guides/average-
| bill.html
| Scott_Helme_ wrote:
| I did try to make it clear in the article.
|
| We're powering 2 x EVs, have two adults working from home full
| time, I have a server rack under the stairs, and we have a hot
| tub outside.
| culebron21 wrote:
| How does a household use 1,500+ kWh per month? At my home, we
| sometimes get above 200, in summer with AC we may score 300 kWh,
| but how do you consume 5x of that? Is it heating?
| coryrc wrote:
| Is your heating electric and do you have two electric cars?
| testing22321 wrote:
| 7.8kw on the roof here in Canada.
|
| 7.72MWh for the calendar year produced saving smack on $1000.
|
| $5000 gov grant (free money)
|
| Full remaining install cost covered by interest free loan, so we
| put that money onto the loan for the next 7 years, then get $1000
| a year for the following 20 or more.
|
| Complete no brainer.
| malshe wrote:
| The payback calculation doesn't consider time value of money.
| They are paying down PS40K today but the savings are realized
| over years in the future. But they implicitly assumed the
| discount rate on those savings to be 0.
| antisthenes wrote:
| Yes, if you want to be super precise you have to factor in both
| the time value of money on one hand and inflation & energy bill
| increases on the other.
|
| But very often these will roughly cancel each other out.
| dreadsword wrote:
| So TLDR: spend 40K up front to save 3K per year - could be cost
| effective depending on the functional lifetime of the tesla
| powerwall.
| KaiserPro wrote:
| I have 5kwp panels one tesla powerwall (bought before musk had a
| midlife crisis) and a single electric car.
|
| In 2025 we consumed 6Mwhr, imported 2.7 & produced from solar 5.1
|
| I assume that OP must have electric heating to account for the
| extra power use, or just does huge amounts of miles. its about
| 54kwhr a day consumption.
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