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How big a solar battery do I need to store all my home's electricity?
- vincebowdren 1y agohttps://archive.is/wOP3A https://archive.is/wOP3A (the site seems to be struggling under the load, e.g. not showing images)
- thelastgallon 1y agoA car battery should be enough.
- joemazerino 1y agoNot even close. A typical electric split will take 12a to maintain and that is just the heating/cooling system. Car batteries are meant for starts, not maintenance flow.
- Jeremy1026 1y agoNot for the thought experiment of "I want my summer excess to power my winter usage" posed by the author.
- KaiserPro 1y agoIn the UK you'd need a class D "loi-sonce" to be able to pull the shipping container sized battery trailer for that to work. However, if you were wanting to use pure lead acid batteries for your house, because you'd be doing slow charge/discharge you'd probably be able to get away with just 1100 130ah lead acid car batteries. I mean you'd be optimising for peak current, which isn't what you'd want. However it could be interesting to see what happens when you have ~500mega Amps at 48v. (24Mw would heat your radiators up pretty quick. ) for lithium, then you'd need 12-14 secondhand tesla/polstar batteries, which if they caught fire, might be a challenge to contain.
- giveita 1y ago1100 car batteries might cost maybe $100-$200k and need replacing every 4 years.
- bot403 1y agoDid you take into account that lead acid batteries are recommended to only be discharged to 50% especially when used for solar ? If not thats now 2200 batteries and $200-$400K.
- KaiserPro 1y agoI eyeballed the maths on that. 1100 * 12v*130ah should give you a .7mwh of leeway to not do "deep" discharge.
- mnw21cam 1y agoLead-acid car batteries are designed for high short-term current supply, for starting engines, not longevity. You can buy deep-cycle lead-acid batteries that last much longer, on the order of over ten years. Moreover, lead-acid batteries wear out when you discharge them too much more than by time elapsed, so taking good care of them can make them last even longer. Lead-acid batteries are great for standby storage, where you normally only discharge them a small amount between charging, but then need to use the whole capacity every now and again (for instance if you have a few dull days). LiFePO3 batteries don't take as much wear from cycling, so they usually wear out from time elapsed instead of over-use. It's economically sensible to cycle LiFePO3 batteries as frequently as possible to get as much "benefit" out of the investment. They're great for time-shifting energy production by charging them at a cheap time of day and discharging them when you need the energy at an expensive time of day.
- Ylpertnodi 1y ago"loi-sonce", would be better "loi-sunse". That 'o' is very jarring.
- KaiserPro 1y ago
- rswail 1y agoEV battery capacity is expected to grow to 100kWh. People will park them at home every night, and probably somewhere with a charging point during the day. Smart house energy management should be able to pick up on that usage pattern and use the car battery for the house while making sure the car is kept ready for use. In the same way that wifi/mobile/satellite comms can keep us "always connected", the changes in power generation and storage are going to keep us "fully charged".
- nxm 1y agoThe cost here is premature degradation of the battery due to additional charge/discharge cycles.
- heresie-dabord 1y agoA house might use 20 to 30 kWh each day. Modern EVs have enough battery capacity to power some appliances for many days. Vehicle-to-load ("V2L") is currently offered in vehicles made by Hyundai, Ford, GM, Volkswagen, Volvo, Mitsubishi and Nissan (the new LEAF). Vehicle-to-grid (V2G) is more ambitious. https://en.wikipedia.org/wiki/Vehicle-to-grid https://en.wikipedia.org/wiki/Vehicle-to-grid
- elric 1y agoAt which point does this become a huge fire hazard?
- hdgvhicv 1y agoA friend has his own battery setup in a shed. He has a ton of sand above it which would collapse in the event of a fire. I have 1000 litres of heating oil in my back garden which is hardly unflamable. 10MWh of fuel.
- SoftTalker 1y agoHeating oil in a tank is quite safe. It doesn't evaporate rapidly, and will not burn unless atomized or spread out. It won't explode unless provided with a much richer source of oxygen than normal atmospheric pressure air.
- mr_toad 1y agoCan LION battery fires be smothered? Online articles are contradictory. Some say they can be smothered, but others say that they generate their own oxygen, and you need to cool the fire, some say to do both.
- GaggiX 1y agoLFP cells are used in these batteries, they are not the same chemistry as the li-po you find in smartphones.
- bob1029 1y agoPretty quickly. There's also a point where it becomes a serious explosion risk too. Every other fire you can stop if you're right there and you catch it. If a battery pack starts to go, you might have a few seconds before the local environment is incompatible with life.
- pjc50 1y agoPeople are used to having 25MWh of heating oil tanks in rural locations, although those are supposed to be stored away from the house.
- rswail 1y agoI think this is something that may happen in the next decade. The interesting impact will be on the grid itself. Why connect to the grid if you are self-sufficient? Then the grid starts to degrade due to lack of maintenance, and the people that can't afford local storage become dependent essentially on a government maintained service. Or should we be planning localized storage and grids at the same time, so we get the benefits of both scale and resiliency and redundancy. People will be parking a mobile 100kWh battery at their house every night. We need integrated V2G and grid upgrades to make the most of this opportunity.
- destitude 1y agoI'm fully off grid today with no issues, even had power company remove power poles. I do heat with wood however. AC in the summer is no issue since that is when I get the most sun anyways.
- dboreham 1y agoImagining you combining these by burning the power poles..
- mr_toad 1y agoIf local storage becomes cheaper than the grid but some people can’t afford it (why, capital costs?) then the government would be better off addressing those capital costs directly. However, you need to consider industrial and commercial use as well as domestic. Can you power a smelter using local solar?
- __d 1y agoProbably? https://reneweconomy.com.au/solar-battery-deal-for-giant-smelter-is-a-stunning-game-changer-for-australian-energy/ https://reneweconomy.com.au/solar-battery-deal-for-giant-sme...
- kccqzy 1y agoI do not think this will happen. Getting most households to be self-sufficient is probably not as cost effective as centralized grid. One there's the economy of scale. Second, any peaks and troughs will generally be balanced out between households and the overall buffer (aka reserve) needed could be lower.
- pyrale 1y agoA small addendum on the conclusions: - every household, can do that, _if_ they have a roof. appartment buildings may not have enough roof for all the people in it. - for those who can't access that, (that includes people, but also the industry, your mobile phone provider, etc.) prices will get worse. - the fire brigade will love industrial-size battery fires in the neighbourhood.
- oezi 1y agoSolar and renewables in general are starting to reduce generation costs. So once the improvements in power transmission are done prices should come down for everyone.
- pyrale 1y agoSolar and renewables alone don't make a grid. You would also need grid-scale batteries, and the cost is not the same. The "improvements" in power transmission is about building more lines, these lines are not going to be significantly cheaper to maintain than previous generations, and if these investment/maintenance costs are shared among less, that means more expensive electricity. Currently, in my country, electricity transport and distribution are about one third of total cost.
- oezi 1y agoYou have to consider that electricity will be 3x over the next 50 years (for transportation and heating). So we are currently building out a lot of extra infrastructure. Grid scale batteries will also primarily reduce cost by offering arbitration.
- jszymborski 1y agoGermans seem to be rather fond of balcony solar https://en.wikipedia.org/wiki/Balcony_solar_power https://en.wikipedia.org/wiki/Balcony_solar_power
- mynti 1y ago
- Bender 1y agoThat is a trick question designed to make people argue and feel like there is some science or math to it. There is not. Nobody here can accurately predict weather far out enough to be a factor in this decision. The truth will vary by demand by family which may have variability throughout the year or decade. Another variable is the number of cloudy days which will vary as climate changes. The answer is somewhere in the neighborhood of as much as one can safely store and afford accepting that batteries have a short life. Much like wells in cold climates the batteries should be in an underground insulated vault made from higher quality concrete as to keep fire hazards away from the home. That is also where whole-home generators and fuel belong, in their own vault so they can be easily maintained without having to rent an excavator to dig out the tank.
- destitude 1y agoEven on cloudy days you can generate power. Unless it is very thick clouds I generate enough for my base loads even in complete overcast skies because I have an "excess" of PV panels.
- Bender 1y agobecause I have an "excess" of PV panels. Which aligns with as much as one can afford. If one calculated an exact amount they would not be able to get the results you are getting.
- SideburnsOfDoom 1y ago> "excess" of PV panels ... aligns with as much as one can afford. does it? Panels are not the most expensive part of the system any more. Overcapacity of panels isn't the bottleneck any more. Battery capacity or roof space might be instead.
- jacknews 1y agoI'm sure it would be much more cost-effective to have community storage, rather than individual storage, and it would balance the load a lot if some users used more power during th day than at night. I think it's called a 'grid'.
- epistasis 1y agoOf course then you have the collective action problem, and convincing your neighbors that grid storage is actually a real thing that exists. And that grid storage is not of the wrong political partisanship. The box of what's considered "politically incorrect" is getting fairly large these days: https://www.theguardian.com/environment/2025/sep/10/south-dakota-solar-energy https://www.theguardian.com/environment/2025/sep/10/south-da...
- floatrock 1y agoSnark aside, there are examples of community-scale energy infrastructure below grid-scale: see "district heating" and "co-gen plants". Sand battery people have been experimenting with neighborhood-scale infrastructure (though industrial heat uses is a better return on that tech right now)
- jacknews 1y agoI've also seen flywheels used locally. It just makes much more sense to have a big battery where the local substation is, than for everyone to install megawatts of battery individually.
- spzb 1y agoIn a manner of speaking, the grid is already the storage mechanism. In summer you sell the excess to the grid; in winter you buy it back. Obviously you pay more to buy than you get for selling but that's the premium for using someone else's infrastructure. You'd spend a load more buying a battery the size of a small house.
- MisterTea 1y agoI always thought about this myself in terms of personal sized long term, high density energy storage. Compressed hydrogen with a fuel cell is the obvious solution. Excess electric is used in a electrolysis cell and a matched compressor fills a bank of storage cylinders. More cylinders = more storage. Though likely very inefficient with a risk of fire or explosion. Are there any other long term high density electric storage technologies that can fit in someones basement, garage, or even apartment closet?
- fdsfdsfdsaasd 1y agoCompressed hydrogen is no joke. It can escape most containers, actively degrades many grades of steel, has a very low ignition energy, and will explode over an enormous range of air/fuel ratios. Definitely not something to keep anywhere where you care about the roof :)
- Tade0 1y ago> Compressed hydrogen with a fuel cell is the obvious solution. To achieve volumetric energy density of hydrogen at room temperature that's on par with batteries (and that's charitably assuming you're using inefficient resistance heating with batteries) you need to store it at a pressure in the order of 100 bar. You're better off with batteries realistically speaking.
- jeffbee 1y agoNobody would even blink if a rural home had a 500 gallon horizontal propane tank, and that represents 20x the energy content of a 1MWh battery pack.
- fdsfdsfdsaasd 1y agoIt would make me nervous, although that's only due to my engineering background. In any case, it all depends on what you want to stand next to. A large explosion, or a multi-day metal fire releasing clouds of hydrogen flouride.
- BobaFloutist 1y agoIf the metal fire is over multiple days, you can walk away from it. The large explosion can kill you before you know there's a problem.
- fdsfdsfdsaasd 1y agoTrue enough, but I'd want to be a lot further away from a lithium fire than from a propane explosion.
- BobaFloutist 1y agoI think there's kind of a local minimum where you need to be farther from the propane explosion, but after your outside the blast radius you're fine, but less so for the lithium fire
- ooterness 1y agoRelevant video from USCSB, from a propane explosion in 2007 that killed four people. https://youtu.be/JzdnUZReoLM?feature=shared https://youtu.be/JzdnUZReoLM?feature=shared
- bluGill 1y agoWhy go for a bigger battery when you can just put more panels on the roof to cover those winter days and waste the power the rest of the year? I suspect the answer is somewhere in the middle - maybe two weeks of storage. Though of course prices change all the time so the correct action will change and you need to rerun the numbers as things degrade to decide your next action.
- pandemic_region 1y agoIn our part of the world, solar production during winter is incredibly low or 0 due to it being very cloudy, days being much shorter, sunlight angle on the panel very suboptimal. No amount of additional panels will get you through that streak.
- yurishimo 1y agoIt also depends somewhat on how much energy you use. I live in the Netherlands where everytime I bring it up, I'm told "that's just not possible, you will never make enough in winter", but these same people have no idea how much energy I use. On a bad day, I use maybe 10kWh and that's running the AC with the thermostat set to 19c overnight and a bit during the day at 22c. I don't have a giant fridge, I don't have any gaming PCs slurping 200W on standby, etc. My baseline usage is around 300-400W to run the old freezer that never turns off (70W), my network equipment, a fan in the garage to prevent moisture buildup, and some lights. My 1.8kWh system at 20% output covers a great percentage of my baseline usage during the day! I'm probably going to add a small battery so I'm not penalized for sending energy back to the grid, but I'm not gonna need much until my kids get older and want new gadgets. The cool part about modern electronics is that we're generally getting more efficient too with newer tech. If I replace the old freezer, my baseline usage drops 20%+. I don't disagree with your point that sometimes nature is simply just working too hard against your efforts, but I also wrote all this to say that some people need to really do the math and not rely on "common knowledge". Energy efficiency has come an extremely long way in the past decade and much of what was true when residential solar first started popping off is now outdated.
- 1y ago
- dgacmu 1y agoAn odd thing about this article is that it ignores the deeper question: what balance of solar over-provisonioning + battery would most cost-effectively cover anticipated yearly needs? I suspect that something like 3x'ing the solar (under 100k) would then let the author get away with much, much less battery, and result in a net cost savings.
- scotty79 1y agoI think he can't imagine 3x'ing because he already has his house covered and only the shed roof remains empty. But that is a super interesting question that immediately comes to mind. I am pretty sceptical about batteries and see overbuilding renewables plus bitcoin mining to monetize excess as a more viable solution.
- NoLinkToMe 1y agoYeah seems like a relatively simple maths/econ problem to solve for, given some parameters like local solar power per m2 in the various seasons, electricity use in the various seasons and time of the day, and LCOE of solar and battery storage. My guess is the differences in either choice aren't huge, as both solar and battery storage keeps getting cheaper. Having an electric vehicle can really help, also. It basically soaks up excess solar power of an outsized installation during much of the year (making the payback time on the outsized installation very good), and can be charged away from the house during a few low-chance bad winter days when the outsized installation is enough to power the house but not the car. Electric cars are charged fully about 3 times per month on average in the US, so working around that with smart charging is not a complex challenge in the next decade.
- superbaconman 1y agoI'm considering buying enough batteries for my day usage, then recharging off the grid during off-peak hours. I can add solar later on.
- kevin_thibedeau 1y agoThe panels are the cheapest components. If you're incurring all the costs to retrofit your electrical panel with an inverter + batteries, you may as well implement on-site generation from the start to recoup more of the costs.
- newyankee 1y agoThe thing is LFP or Sodium ion are both expected to have 5000+ useful cycles soon (or possibly even in production now). This means even if you use one full discharge overnight , this is like 15+ years of life of the battery, although I suspect calendar degradation will be much faster. Higher the cycle life, lower the levelised cost of storage and this is what matters in my opinion. Best is to have some type of long term storage like a Diesel generator only for estimated 1-2 weeks of the year depending on location where it will be needed. I feel V2G with 3 days backup and a house low power mode which can be utilised in emergencies might solve even this issue. Oversizing solar to the extent possible for winter loads is also ideal because so far that does not seem to be the driving cost.
- epistasis 1y agoNo, LFP is 8k-12k cycles, and sodium are expect to be 15k to perhaps 20k cycles. This is reflected in the manufacturer warranties, and many sources. Here's one: https://www.volts.wtf/p/whats-the-deal-with-sodium-ion-batteries https://www.volts.wtf/p/whats-the-deal-with-sodium-ion-batte...
- newyankee 1y agothat makes calendar aging the limiting factor even more. I feel that so many cycles can also aid in smoothing solar & wind (at turbine level) output and increase their utility. I feel that long term energy storage will be split between thermal and non thermal in interesting ways and the market for them will open up after first level of daily disruption
- epistasis 1y ago20,000 daily cycles if 55 years. 10,000 daily cycles is 27 years. The expected usage case for these batteries is near daily usage. I hadn't really thought about thermal tech in such extreme terms until your comment, but to me it appears to be the tape storage of our times. There will always be a fair amount of infrastructure hidden that almost nobody knows about, but it's going to be dwarfed in active usage by HDDs or SDDs. The tech advantages really are that big for batters and other solid state energy tech over the moving parts thermal variety. Thermal tech hasn't had an upgrade like LTO-6 (or is it 7 now) and is pretty much at the end of its possible engineered capabilities, but batteries are just barely getting started on what they are capable of.
- SirFatty 1y agoWhy worry about panels and batteries when you can have an Egg? https://enron.com/pages/the-egg?srsltid=AfmBOoqW03cqyIhQ0OlGnEgd7L1xu87PjzVIcLtUmOf8CdH8qxEk_b-H https://enron.com/pages/the-egg?srsltid=AfmBOoqW03cqyIhQ0OlG...
- gnfargbl 1y agoSomething that isn't spoken about enough is that in developed Western countries, grids are actually significantly oversized due to reductions in electricity usage over time [1]. That link says 16% over, but the peak demand in the UK in 2024 was actually only 45MW [2], which I make more like a 30% reduction from the all-time peak. Because of this, it feels like we should already have enough transmission capacity in a decent part of the network to cope with a re-organisation of where the sources and sinks are placed. Yes, we might need to do some work in the last mile, especially if V2G takes off, but things aren't nearly as bad as one might naively assume. [1] https://www.nationalgrid.com/stories/journey-to-net-zero-stories/can-grid-cope-extra-demand-electric-cars https://www.nationalgrid.com/stories/journey-to-net-zero-sto... [2] https://www.neso.energy/news/britains-electricity-explained-2024-review https://www.neso.energy/news/britains-electricity-explained-...
- pjc50 1y agoThe trouble is the capacity is in the wrong place; the UK closed coal plants in (defunct) coalfields in the middle of the country, and built offshore wind farms which tend to be further north. There's plans for an offshore north-south connector to help with this.
- gnfargbl 1y agoTrue, but don't forget you can put BESS on the sites of the old coal plants: https://www.bbc.co.uk/future/article/20240927-how-coal-fired-power-stations-are-being-turned-into-batteries https://www.bbc.co.uk/future/article/20240927-how-coal-fired...
- dboreham 1y agoThat connector goes underwater right where I grew up. I haven't visited mother for a few months but afaik they haven't begun digging yet.
- oezi 1y agoElectricity needs are expected to rise significantly as we convert heating and transportation to electric.
- PinguTS 1y agoThe HTW Berlin has a autarchy calculator. Unfortunately only in German language: https://solar.htw-berlin.de/rechner/unabhaengigkeitsrechner/ https://solar.htw-berlin.de/rechner/unabhaengigkeitsrechner/ They also test and publish yearly the latest battery combos.
- destitude 1y agoIn case you didn't realize he is looking to store ALL of the summer generation into a battery and generate zero power in winter.. so rely entirely off of a battery during winter.. which is absolutely no feasible for a normal person and nobody would ever do.
- fdsfdsfdsaasd 1y agoI once did a related calculation on "How much of my garden do I need to dedicate to coppiced willow to heat my house for a week per year?" I concluded that we're all going to need much bigger gardens.
- IshKebab 1y agoStoring energy from the summer for the winter is a really inefficient way to do it. It's much better to massively over-provision the solar so you have enough energy - on average - for the winter. Then you only need a couple of week's worth of storage to account for extended cloudy periods. Much cheaper, and you get a ton of extra free power in the summer. The only downside is a typical house roof doesn't have enough space. But a typical house doesn't have enough space for a 1 MWh battery either so...
- freetime2 1y agoYup if you really need to be off grid in a climate that has cold, cloudy, snowy winters, you’re probably going to need a generator that runs on fossil fuels. For everyone else, use the grid.
- ViewTrick1002 1y agoOr run it on biofuels.
- ortusdux 1y agoWoodgas would work as well
- mnw21cam 1y agoAgreed. You can increasingly over-provision the solar generation to reduce the proportion of time when you will need a fossil fuel generator or grid input, and install lots of battery to allow the system to smooth over multiple dull days. But chasing that 100% is going to be very expensive, and at some point it'll be much cheaper to have a fossil fuel generator that you need to run 1% of the time.
- mrexroad 1y agoYeah, w/o grid fallback, I’d much rather aim for 98-99% w/ solar and have an alternate source to close gap, rather than aim for “five 9s” on solar+batt. It’d take a lot to talk me out of a multi-source approach.
- morninglight 1y agoYou might want to factor latitude into your calculations. https://www.recurrentauto.com/research/winter-ev-range-loss https://www.recurrentauto.com/research/winter-ev-range-loss
- deleted 1y ago[deleted]
- philjohn 1y agoIf you just want to come out cost neutral, the battery required is far smaller when paired with a large enough array, and a time-of-use tariff. With 3 EV's in the house, and a 12.8kWp array, with a 10kWh battery, charging overnight in the winter on the cheap EV tariff (7p per kWh vs 27p per kWh) and exporting during the spring, summer and autumn at 15p per kWh I'm seeing an electricity bill of below 0. Of course, with a shift in energy production to renewables, all of that maths may get upended, but for now, I'm going to break even far before my original estimates.
- sensecall 1y agoI was trying to work this out the other day and ended up building a thing because I couldn’t find anything similar from the energy companies: https://energybillcalculator.sensecall.co.uk/ https://energybillcalculator.sensecall.co.uk/
- dylan604 1y ago> Of course, with a shift in energy production to renewables clearly, you're not in the US as renewables are considered the problem here and not part of the solution. i'm waiting for the administration to come out with clawback plans for all of the subsidies for home solar and even the EV subsidies. gotta pay for those tax cuts some how
- syncsynchalt 1y agoPoliticians make a lot of noise about renewables but they're still being installed by grid operators record-breaking numbers, including in places like Texas. Renewables pay for themselves and the lack of federal incentives no longer slows the rate they're being installed.
- epistasis 1y agoOne of the most important new types of renewable, deep offshore wind, is just becoming very economical, and was on the precipice of being deployed at large scale in the US. However, Trump has issued stop-work order on the only two projects, both multi-billion dollar, with issued permits. They are the ~800MW Empire Wind Project and the ~700MW Revolution Wind project: https://www.utilitydive.com/news/trump-administration-offshore-wind-revolution-wind-orsted-stop-work/758500/ https://www.utilitydive.com/news/trump-administration-offsho... https://www.canarymedia.com/articles/offshore-wind/fishermen-oppose-trump-revolution-halt https://www.canarymedia.com/articles/offshore-wind/fishermen... The Empire Wind project was allowed to continue after negotiation from NY's governor, but these sorts of mafia tactics will stop the development of new off shore wind projects. Multi-billion dollar projects getting shakedowns midway through is no way to run a country. Perhaps even worse, it prevents the US form acquiring the construction skills to work on this on our own in the future. We are getting extremely far behind on a crucial technology for renewables at the population centers for northern latitudes.
- jhallenworld 1y agoAnother way to look at this: how much solar do you need to synthesize 1 MWh of methanol ("e-methanol") from water, which is only ~54 gallons (200 liters)? Actually you need 135 gallons since the generator is likely 40% efficient (or less..). This is not much fuel, I used to have two 275 gallon oil tanks in my basement. I think e-methanol synthesis is ~%50% efficient, so double the solar. Doesn't sound so bad. Now if you could synthesize methane you could push it into the gas grid and run the meters backwards, thereby avoiding the need for storage... actually methane synthesis is even more efficient, >70%.
- fouronnes3 1y agoIf you consider the fact that only half of Earth is experiencing summer while the other half is experiencing winter, there's an obvious madlad solution to instead of storing power, transfer it from the summer hemisphere solar panels to the winter hemisphere electric heaters, somehow.
- k__ 1y agoMight be easier to use satellites to send the sun to the other hemisphere
- soylentcola 1y agoGood thing that could never be used as a "death ray".
- internetter 1y agohttps://www.reflectorbital.com/ https://www.reflectorbital.com/
- lysace 1y agoThey currently most efficent method is called HVDC and it's not really efficient enough to be anyhing resembling economic at those distances. Ohm's law is a thing. Edit: I again made the mistake to comment on a thread dealing with energy x politics. Sorry, I'll try not to do that again. I'm out. It's feral.
- cinntaile 1y agoUHVDC is 2.6% loss per 800km so after 8000km you have 76.8% left. That's not too bad. Although I obviously don't know what distances you had in mind.
- lysace 1y agoBullshit. What voltage is UHVDC at those numbers? Who is supplying the equipment? Where are the demo installations? What's the cost? Again, the goal is economic very long distance transfer of electric power. Not a Chinese university research project.
- buckle8017 1y agoSo this basically just shows that his solar panels are subsidized by the grid at whatever the depreciation rate is on 1000kWh of batteries. which being very approximate is 15k gbp/year
- 1970-01-01 1y agoCrashing panel prices, output degradation, local and state laws, and most importantly, bidirectional charging should all play into the long term calculations.
- __alexs 1y agoCan't shake the feeling that domestic PV is a con designed to try and shift responsibility for the climate crisis to consumers rather than industrial energy providers. The ROI of a large PV farm must be substantially better than a home scale install.
- hectormalot 1y agoIt depends. 80% of my electricity cost is taxes. If I produce it using PV, the consumption is never taxed, and the benefit is pretty substantial, on top of the market electricity price. (One rarely finds low risk investments that return 20-25% year)
- gertlex 1y agoCurious where you are roughly located; Does that 80% include the distribution of the electricity? Should I interpret the 20-25% returns as being, your annual savings on the utility bill are 20-25% of the cost of your PV install?
- hectormalot 1y agoNetherlands. No distribution fees are separate. Roughly speaking the electricity is about €0.06 with about €0.20 in taxes on top. So offsetting consumption nets me about €0.26 cents per kWh. The installation of a 2800kWp system cost me about €2600 and generates between 2400-2750kWh annually, so about €650 euro. In a 10 year timespan that’s an IRR of 20%, creeping up to 25% for 20 years.
- gertlex 1y agoThanks for the numbers! I had no idea taxes were such a large fraction elsewhere. Good to know/consider. I'm most familiar with California. (and actually can't give a % that is taxes offhand) After the first year of having PV, I determined my own payoff time of about 5-7 years, so that was nice and self-justifying, and haven't dug deeper into details on that.
- 1y ago
- binary132 1y agoThis type of thing would really need to be implemented at the township / local community level at least, similarly to how every house doesn’t have a big electrical substation plugged into the high-voltage power mains with explosive oil-cooled transformers. It’s simply not realistic to think every private dwelling can or should have this kind of capability, to say nothing of the cost. Maybe large communal housing could. Ultimately it’s a sort of social optimization problem and I don’t think giant individual capacity solves it efficiently. One thing that could possibly work better IMO is something like a small local renewable fuel economy where excess power is used to produce hydrocarbon fuel by catalysis of electrolyzed hydrogen with carbon sources, and individuals can purchase this fuel to recover the energy, or possibly the power plant could use it during solar lows. The advantage of this type of system is that it’s not really capacity limited, as long as you have enough fuel storage, which is simple to build more of. of course, you could just use alcohols distilled from fermented plants instead, but that’s not as sexy.
- bdamm 1y agoWhy liquid fuels or chemistry at all? Something simple like moving blocks of cement uphill with a motor/generator would be more efficient.
- jakobnissen 1y agoDo the math on energy density. 1 kg of fuel contains roughly 45 MJ, which would require you to lift 1 kg of cement 4.000 km up. Or, alternatively, 1 liter of petrol has enough energy to lift a 3 tonne cement block 1 kilometer upwards.
- epistasis 1y agoRun the numbers and you'll find that blocks of cement are pretty expensive compared to the batteries! Over the past decade there's been several startups trying to do gravitmetric non-hydro grid storage, and even with favorable conditions (e.g. a large free train track on the side of a mountain) they can't get the economics to work. Plus, that tech is never getting cheaper, like batteries are every day.
- 1y ago
- whitehexagon 1y agoIt's an interesting thought exercise, but the quick short term solution would be a 5kWh buffer battery just for the evenings to save buying at peak times. I started that way before going fully off-grid to avoid subsidising the fossil fuel industry here. Plus ~70% of my bill was fixed charges, and they wouldnt pay for excess solar generation above what I used. I think this sort of mega home battery bomb could be avoided through legislation by offering free grid connections. So I 'pay-in' 10kWh today, and maybe my account is credited with '5kWh' for later use. I'm sure we would see a much bigger uptake of home solar with such a scheme.
- Taek 1y agoLook up "net metering" or NEM, this is already a thing in many jurisdictions.
- Loughla 1y agoAnd in many jurisdictions they're putting time limits or just straight up eliminating net metering and replacing it with net billing. So instead of 1:1 credits, the power company buys it from you at what they would pay their producers (read, several times less than what they charge you). It's a fucking scam. My power company limits the size of panels and time limits net metering (they don't even do it anymore for new solar installs). So you can either not do solar or go completely 100% off grid with only one step. It's a fucking scam. The engineer justified it to us when he was signing off on our solar install as "well when we do 1:1 credits c that's like you stealing from your neighbors. They don't want to pay your the full retail cost. They want to pay you what we pay the power producers." When I asked if that meant my neighbors would have the ability to pay less, he just sort of looked flatly at me. An absolute scam. Edit; Sorry, I forgot to add; 1. They also won't allow battery storage while connected to the grid. If they wanted to buy surplus but allowed my to store my own production, I would be fine with it. 2. They also net bill daily. So while I may produce extra within the billing cycle, they zero out excess production daily.
- oangemangut 1y ago
- jillesvangurp 1y agoIt's a nice back of the envelope calculation. I think the conclusions are correct for the stretch goal but it does not make economical sense. Yet (those sodium ion batteries could change that). There are several things you might want to consider: - wind, there are smallish turbines that you can put on your roof that generate a few kwh. Also when the sun doesn't shine. Extended periods without any wind at all are rare. 2-3 weeks would be a lot. That probably drops the amount of battery you actually need quite a lot. - Second hand EVs are relatively cheap and come with some affordable batteries that are probably larger and cheaper per kwh than most commercial domestic storage solutions. Not for everyone but if you can wire things together, that might not be a bad option. Especially if you can get ,a good deal on some well used EV with a half decent battery. Relatively low loads might increase the life that battery has if you just use the car for storage. - You don't have to generate the power next to the battery. Some cars can provide power to your house; when your house battery runs out, you can just use public chargers and drive back and forth to top up your house batteries. A bit of a chore but probably better than investing in batteries you don't need most of the year. Not a bad option if you live off grid. Batteries on wheels in general are a thing. Electrical semi trucks come with > 500-600kwh typically. That's a lot of power that you can move between your home and your charger. Container sized batteries are a thing. If you want to, you can get about 3-4mwh on your property. It's not going to be cheap. But it's doable. The point here is not that you can have a huge amount but that you could stretch a modest amount quite far by simply driving to and from the charger. Of course if you have a grid connection, using that is more convenient and cheaper. - The capacity factor of your batteries is going to be a function of how often you cycle them. If you rarely cycle them fully, they are going to be relatively expensive. So, while hoarding batteries might make you feel nice and comfortable, it's not a great economical choice to make until batteries become a lot cheaper. - The money you save on not paying for grid power needs to be balanced with the cost of a battery and how long it will last you (10-20 years?). If your monthly bill is 100, you might spend 1200$ per year and 12000$ for 10 years. So, that's your budget for a huge battery. If you factor in that it will have a low capacity factor, it might last quite long. Twenty or even more years. I have a lithium ion battery screwdriver that's nearly 20 years old; still fine. Because I rarely use it. So your budget could be 20-30K$ Adjust as needed based on grid prices and usage. - As others mention, generators are relatively cheap and they do work if you can stand the noise and exhaust fumes. Not clean. But relatively cheap. It's a valid thought experiment to repeat until the cost adds up. Your opportunity cost while you don't invest in this stuff is basically what you will continue to spend on the grid. Which is probably not horrible for most people. Until those cost curves cross, you are better off waiting. Or compromising and buying a battery that won't solve the whole problem but is cheap enough that it will earn itself back in a reasonable time. It's trade off between need and cost. If you absolutely need to be off grid, it's doable if you have the space and resources. But it's not going to be cheap. Until then, some hybrid solution is probably more optimal.
- mschuster91 1y ago> Remember, this is just a bit of fun. There's no practical way to build domestic batteries with this capacity using the technology of 2025. Huh? A single Tesla Powerwall 3 stores just about the same 13.5 kWh the author describes as being the battery size they need [1]. And they are by far not the only ones offering ready-to-install battery packs. Fully electric vehicles with vehicle-to-grid wallboxes enable even larger systems. [1] https://www.tesla.com/de_DE/powerwall?redirect=no https://www.tesla.com/de_DE/powerwall?redirect=no
- natmaka 1y ago> In the last decade lithium ion battery prices have fallen 90% The price of batteries has declined by 97% in the last three decades: https://ourworldindata.org/battery-price-decline https://ourworldindata.org/battery-price-decline
- Taek 1y agoIn the category of doing obnoxious things for shock value, why stop at merely making sure you have enough batteries to keep you covered during the *average* year? Why not make sure that your home is going to be fully self sufficient in 99.99% of years? That probably adds another 50-150% to the total amount of storage that you would need. But also, the expensive thing about batteries is typically the amount of power they can produce. The post used lithium ion batteries as a reference point, and those typically have a power rating between 1 and 4 hours - meaning they can fully discharge an entire summer's worth of stored energy in 4 hours... which is probably not something you need to pay for. If you want a ton of really cheap long term energy storage, you'd look into a technology more like hydrogen fuel cells. The raw power (for standard home, 10 kW is plenty overkill) is going to be more expensive than lithium, but for storage you just need a bunch of hydrogen stored somewhere safe (probably buried underground in your yard). That's much, much cheaper than lithium ion batteries on a per kWh basis, especially if you are scaling up into the MWh territory. And, the other big cost saving solution is to just add more panels. It means you'll be overproducing in the summer and you'll have to curtail, but some curtailment in the summer is a lot cheaper than finding a way to ferry all of that energy into the winter. Then you have extra panels in the winter and you don't need as much storage to be fully self sufficient.
- tpm 1y agoStoring hydrogen at home is not going to be cheap though, is it? At that point it would be worth to look at storing eg methanol.
- BizarroLand 1y agoUse heat and pressure and electricity and you can convert CO2 and Hydrogen into Methane. Methane when burned releases the CO2 back into the atmosphere, but if you're mining the CO2 from the atmosphere to begin with it pretty close to carbon neutral fuel. https://news.osu.edu/turning-carbon-emissions-into-methane-fuel/ https://news.osu.edu/turning-carbon-emissions-into-methane-f...
- cobbzilla 1y agoit would also be really cool to use excess power generation to drive atmospheric petroleum synthesis (pull carbon from air to make hydrocarbons); then sell it or store it for later use. I know the tech is not quite there yet, but it’s getting closer every year.
- yesdocs 1y agoI have at Tesla system with 3 batteries, and I argued during installation to include 8kw of panels situated on the west side of our roof against Tesla ‘s engineering. The panels would only by 72% efficient on the west side as opposed to 74% on the east side (catching the morning sun). But my modeling showed that we would exhaust the batteries in the evening due to the fact that my usage was higher in the late afternoons and it wasn’t offset by any generation of solar panels during those late afternoon hours. After modeling scenarios based on historical usage PER HOUR, I was able to show that if we had enough solar generation during peak late afternoon hours, we would be able to ‘survive the night’ on batteries until morning solar generation resumed. This means my 14kw solar panels coupled with 3 batteries gets me completely off grid for 9 months out of the year. That’s not bad considering I get 7ft of snow during winter months and I am surrounded by very tall trees. Optimize on hourly generation not daily, most solar companies use DAILY numbers without a clue on hourly usage. I currently get 0.08$ for every 1$ in electric production, so there is very little benefit in producing electricity when you don’t use it. Optimize your system based on your usage not on DAILY production. If electric companies would give me credit of say 0.90$ per 1$ then the equation changes, but electric companies would rather benefit from your overproduction, be careful as these systems are not cheap!
- jhickok 1y agoThank you for the example. I am always interested in real-life stories from other snow-laden users.
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- ortusdux 1y agoWhat do you use for heat?
- kridsdale3 1y ago
- duffpkg 1y agoI have a home in the southwest that is offgrid and runs entirely off solar. It has a 43kwh battery that covers 100% of it's needs including AC. It has a 4kw solar array. The batteries shipped to your home inclusive of all taxes and fees, UL listed, are only $5,400 today from a variety of reputable suppliers. This is obviously different than urban london but I wanted to point out just how economical this is for huge swaths of the country and how absolutely absurd some of the pricing I see on things like tesla powerwall are. Note: There are a lot of components to an installed battery system that effect pricing such as racking, wires, busbars, breakers, etc, etc. I am referring only to the enclosed battery units with BMS.
- jorblumesea 1y agohow are you able to charge 43kwh on such a small array? we have a 12 kwh setup and it recharges a 15 kwh battery in a few hours.
- duffpkg 1y agoIn that part of southwest there are only a handful of cloudy days per year and at a relatively low latitude.
- lnsru 1y agoWhat’s the charging/discharge power of your battery? Is it AC or DC coupled?
- duffpkg 1y agoMy battery is 3 separate "48v" x 280ah units in parallel. There is no grid so I am not sure what you mean by coupled. The batteries output DC to inverters which output AC. It is several years old at this point, probably the better value is in "48v" x 320ah setups now. The breakers/busbars, etc are setup for max discharge of 200A but in practice I have never gotten anywhere near that.
- lnsru 1y ago
- j45 1y agoI know batteries to generally be safe but am wondering if any folks are putting the battery systems outside of their home, let's say in a shed, detached garage, or a purpose built enclosure for batteries?
- kevin_thibedeau 1y agoIn a cold climate you have to add heating and an insulated enclosure to keep them alive.
- BizarroLand 1y agoBury them below the frost line in a concrete box with a sealed access port, add in some water cooling for when the battery heat goes above a cutoff. They'd never get too cold that way, stay around 60 Fahrenheit by default.
- edent 1y agoWe have ours in a porch - mostly because the fan is slightly noisy. I think the main consideration for any outbuilding would be whether it was water-tight, had some level of climate control, and was secure against theft.
- j45 1y agoThanks, I think I saw some reference somewhere to consider the lithium in the batteries and safely keeping them in any space. This would remain relative to climate and security needs though as you're pointing out.
- metalman 1y agogoing forward, solar pv and batteries will continue to get cheaper, but each house will vary quite considerably in how to maximise and optimise things for what will always be an exercise in averages that is modified by whatever contingencies are included, and after living off grid for decades I could care less and recomend careing less about the math, start now with something modest, iterate,learn, end then install the largest system that you can. If you are going to build new, start with site selection, plan for car charging, and use all of the best practices for integrating passive solar into the homes structure.ie : homes built with double walls and a thermal break require NO home heat source as normal domestc activities will generate excess heat that must be vented. Anywhere north or south of 30° design should be for bad weather in the winter, and the rest of the year will almost certainly be gravy. For all refits and renovations to solar, the math will always be ,the most that will physicaly fit. Regulatory limitations will most certainly restrict batteries to a day or two backup in most situations.In most jurisdictions, a large battery would require a seperate building with significant set backs to any structure, untill we get to solid state non flamable batteries, which may be on the horison now.
- themafia 1y agoBatteries self discharge. There is no system that will hold 100% charge for several days.
- edent 1y agoIt wouldn't need to. It would start discharging at sunset and only stop at sunrise. And in winter it would spend most of its time discharging. But, as I say in the post, this is a bit of fun looking at extremes.
- SubiculumCode 1y agoLet me guess why this is coming on, its top-up time on our solar energy bills. Those transport fees on externally sourced electricity sucks.
- 0xbadcafebee 1y ago> What I want to do is find out what the maximum size battery I would need in order to store all of summer's electricity for use in winter. This is ridiculous. It's like asking how much propane do I need to store in summer to go the whole winter? You would need a tank so big it could fill up propane tankers. Thus why we get regular deliveries of propane throughout the year on an as-needed basis... and why you should only have enough battery to store the peak energy use for a couple days at most. If you have an extended period of no sun, first you reduce your energy use, and then you top up with a generator. This is far cheaper and more flexible than having a gigantic battery array for an edge case. 22kWh in battery (self-contained units, BMS, heating element, etc) costs <$4400 in the US, shipped from China, for a reputable (but not pricey-brand) battery provider. More than enough to power most homes (in Northeast US, cold winters without much sun) for a couple days. Add in everything else you need (wiring, solar panels, power inverter(s), MPPT(s), generator, etc) and you get to $6.5k-$9k
- thomas8787 1y agoThe winter months and parts of the fall months are hardest due to a lack of sunshine. Without an EV, from March until late September a 5kWh battery is enough for me to keep my daily grid power consumption close to 0. A 5kWh plug-in battery now costs around 1299EUR. Pays back itself in a handful of years. Batteries are similar to solar panels in this regard. With solar, the first couple of kilowatt-peak delivers the biggest savings. With batteries, it's the same with the first couple of kWh of storage capacity.
- tomekf 1y agoWhat battery you have in mind? Can you share name/model?
- thomas8787 1y agoMarstek Venus E (5.12kWh), this plug-in model has gained a lot of popularity the last couple of months in some European markets like Belgium, Germany, and the Netherlands. It has a maximum charge rate of 2500W and can discharge at up to 2500W (should be connected to a separate power group and only if local regulations allow it). These kind of batteries plug into a regular AC socket and do not require an electrical inspection. But they aren't legal everywhere. In my case, it's configured to track the readings of my digital electricity meter. The battery charges itself when my solar panels produce excess power and discharges when it detects grid consumption. Throughout the day, it buffers the intermittent solar power, and during the evening, night, and early morning hours, it keeps my grid power consumption close to zero.
- johnea 1y agoI'm in the middle of a renovation now, that will include batteries and solar. One thing that I never see mentioned is how to support on-demand instant hot water heaters. The 6.5 gal/min heater (what it takes to fill a tub) that I'm installing uses 100A at 220v when operating! I haven't found any battery system that can support that. Do "totally off-grid houses" all use a typical electric storage tank hot water heater? For my solo occupation, that's a lot of hot water storage over times when almost none is being used. I do have a smaller water heater under the kitchen sink, so that the giant one doesn't have to run for that usage. How do off-grid homes deal with the high instantaneous current consumption of on-demand water heaters?
- edent 1y agoThey don't. You either have a solarthermal system to heat the water, or you use a tank to store hot water. I've previously installed an "iBoost" which diverted excess solar into an immersion heater. Heating slow(er) and storing is going to be easier than suddenly ramping up for a shower.
- testing22321 1y agoFor decades off grid setups have not used electro heat water or air, it’s just too energy intensive. That is changing a bit with the price of panels and batteries falling so fast, but it’s still not the most common option.
- gwbas1c 1y ago> It is possible that, not too long in the future, every home could also have a 1 MegaWatt-hour battery. They would be able to capture all the excess solar power generated in a year. Seems like we'll get to a point where adding extra panels "makes economic sense" long before this kind of storage makes sense.
- jasba58 1y agoIf you want 100% GHG reduction, for every 1 watt nameplate solar rating, 1 x 0.2 capacity factor x 730 hours a month x 3 months a season = 438 Watt-hour of battery or other energy storage. 80% reduction needs 100 hour vs a whole season, so 20 watt-hour required storage. Dr. Chu of Stanford is my source.
- dhosek 1y agoI’ve been puzzled by a number of houses near me with panels on the north-facing roof. Are panels really that cheap that it makes sense or are people that stupid?
- jansper39 1y agoI can get 450W solar panels near me for around £55(~$75) so yeah they're pretty cheap. Makes sense to cover the roof while you're up there.
- testing22321 1y agoIn many places it’s cheaper to build fences and walls with solar panels than traditional materials. I want to make my next roof out of them directly
- thelastgallon 1y agoI wonder if compressed air energy storage systems can be built for homes. It can be a tank part of the foundation. Too small CAES doesn't work, too large may get messy, but a house size tank might be best.
- hunterpayne 1y agoIf you don't live at some combination of high altitude, low latitude and low cloud cover then don't do this. You will never pay off the CO2 produced in making your installation. So it does more harm than good. This isn't true for all sites, but the large majority of where humans (especially English speaking humans) don't live somewhere where this type of setup doesn't do more harm than good. Mexico City, Santa Fe, places like this are great for your proposed setup. Wherever you likely live, probably not.
- ggm 1y agoFor the right kind of storage, even high loss storage could be worth it, if it is long-duration storage. The problem is economics with for-profit generation, not storage cost: If the cost of generation from PV was equitable, you would "store" your volts in the supply chain and withdraw from the bank over winter. Then the storage (at loss to transport) would be in Dams and other long duration spaces.
- travisb 1y agoIn most cases every residential system is getting payment rates at least that good. The problem is that wH-for-wH doesn't take into account distribution costs, which is most of the residential cost of electricity, and that a wH at noon in July doesn't cost the same to generate as a wH at 2am in February. For most jurisdictions you can look up the large industrial rates to find the wholesale energy rates. Residential solar is worth about half of that 'reliable' electricity rate.
- curtisszmania 1y ago[dead]
- paladinpower 1y agoYou need to look at your power usage, appliances, AC, etc and that will tell how much solar, batteries and inverter size you need. PaladinPower is the only whole home backup on the market. Call them for free analysis and a quote. They even power homes 100% offline, including homes impacted by natural disasters in LA.
- jansper39 1y agoWhat about all the other whole home backups on the market?
- ChaoPrayaWave 1y agoOne thing I rarely see discussed: could we share seasonal storage across neighborhoods? Like a "battery coop"? Centralizing this might be more feasible than each home trying to do it alone.
- bradtemp 1y agoOf course, in most states there is net metering, so it is foolish to store it; feed it to the grid. Storing in a battery will cost you about 15 cents/kWh and more like 30 cents/kWh with Tesla powerwall, so you need to have that large a difference between the cost of power when you store it and when you take it out. It is unusual to have a battery to store all your unused solar output, that would be very expensive. You don't want to store more than you will actually need, and in particular more than you need from 3pm to 9pm or whenever your local high-peak rate is. So it's up to you to measure how much you need then. (You will have solar from 3pm to 5pm or so, a bit later in high summer.) If you seek home backup, generally you don't want to pay to run your home at full load during an outage. Surely in an outage you won't charge your car, or run your over or dryer, or your air conditioner on full etc. Consider how much power you need when conserving, unless you are expecting an apocalypse style outage. Get enough battery for that.
- Zufriedenheit 1y agoI did the same calculation for my home a while back. Came to a similar result: about 0.5M EUR battery would be needed. Also self discharge is a big problem. Probably redox-flow battery would be best for this use case.
- alphabetmedia 1y ago[dead]
- ivanjermakov 1y agoThe question bothering Factorio players since 2016: https://wiki.factorio.com/Power_production#Optimal_ratio https://wiki.factorio.com/Power_production#Optimal_ratio
- veunes 1y agoThe key insight here is how deceptively hard seasonal storage is. It's not just about matching annual production to consumption, it's about time-shifting summer surplus to winter deficit, and that's where things get wildly impractical
- egberts1 1y agoRight off the bat: if your solar panel is underpowered during winter days, no amount of batteries can make up the shortage during night time. It behooves you to ensure that winter solar power exceeds your usage before even to consider buying any batteries. 780kWh/month for 2,000sq 1970 Texas natural-gas ranch-sytle home in December. I would need 1400kWh just to be able to start charging batteries (which includes 780 daytime usage) so that all-night-long nighttime usage are still battery-available/supplied. It gets worse during A/C usage months. Battery-store power for residential are at best transient and temporary. Public ones explode often. I learned all this with homemade battery pack and windmill-powered generation in 1973. Solar cells were pricy then, 10 of those large-stamp-sized solar panel were $166 (in 1973 dollars) and still could not keep one red jumbo LED lit all night long.
- sowbug 1y agoHow about using AI as your battery? When your PV panels are producing excess power during the day, spin up a GPU and rent it out through a cloud provider. Spend the money on the power your home consumes at night.