What a year of solar and batteries saved us in 2025
scotthelme.co.uk
scotthelme.co.uk
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.
Alternatives: https://electrek.co/2025/12/28/opinion-its-time-to-start-rec...
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 $10k, though I did the work myself (which would probably hae been another 3-5k if I could have found someone to do it.
Yo. If you can find an electrician to stop by my house and turn a light switch off for less than 1000$, 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.
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.
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[1] https://www.tdlr.texas.gov/electricians/apply/individuals/jo...
[2] https://www.tdlr.texas.gov/electricians/apply/individuals/wi...
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.
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.
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.
They said it was city code causing their problem.
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".
It took him maybe two hours to run the wire.
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.
Better comparison:
Author's config:
3x Powerwalls + inverters = 40 kWh
4.2 kW array
£39,360 = $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...
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.
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...
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).
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.
It's such an industry term that it's literally a named 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 (120v * 50a) + (120v * 50a) or (240v * 50a). The legs aren't cumulative. You're implying the standing load capacity is somehow higher than its inrush capacity. It would need to be a 24kw (on the ac side, all of the janky chinese rebrand inverters all list their DC input to try to make themselves seem bigger) inverter to do what you're implying.
(50a * 120v) + (50a * 120v) = 12kw
A small home with a smaller 150 amp service is (150a * 240v), 36kw.
Edit: screw it, I'll address this as well -
>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.
There sure is! The whole point is to offset usage. 50 amp standing load capacity means you can only ever offset 50 amps of usage at one time. Sure, most homes don't hold anything higher than that for long but I've seen plenty of homes hold over 20kw for a bit if they have pool pumps, well pumps, pool heaters, or any number of things going on. Any time the home draws more than 12kw instantaneously you'd be getting charged peak rates, which could be avoided with a larger standing load capacity. In addition, if you're in a municipality with a 'demand' rate you could enter in to a different billing rate any time you go over a certain amperage, meaning that ability to offset more of that in that instance, even just for an inrush, could make an even larger difference on your bill.
Look man, I run an $800 chinese inverter, and my batteries are MuRatas I harvested from decommissioned Sonnen cabinets that I rewired with chinese BMSes. The Powerwall 3 is a really good product and the pricing is great compared to comparable non-diy consumer grade products. The EG4 is not a good comparison point because it has nowhere near the spec or capability. You would need 3 EG4 18ks to have the inrush capability of a single Powerwall 3. Battery capacity (volume) is not the sole determining factor in value. This isn't even relevant but just as an aside, the EG4 isn't even a good value for the DIY scene, and has functionally the same support as rebranded drop shipped Chinese inverters.
I would respond to all of your items individually again but its clear by this comment I can't you seriously and now you're just trolling.
I'd rather land wires in a Sol-Ark, it has better support, it has a higher AC output, it has a higher battery charge rate, and it's the same price.
Be gone troll.
https://energylibrary.tesla.com/docs/Public/EnergyStorage/Po...
Just to be perfectly clear on your continued misunderstanding - each powerwall is also an inverter, it has its own AC power output. That stacks. The batteries strapped to the EG4 are all limited to going through the EG4. That means no increased output for adding more batteries. No stack.
With 3 EG4s in the comparison you would have a similar standing load capability(36kw claimed), however you'd still only have roughly 1/3rd the inrush capability(190 amps).
Honestly, I thought I started this conversation nicely enough and went out of my way to be informative and you've only tried to insult me and be snide while having the loosest grasp on the subject matter.
> The original comment is all within your framework of 3 Powerwalls vs one EG4 18K with 3 batteries. That's 12kw AC for the EG4, and 34.5kw on 3 Powerwalls.
And for the last time, you do not need 34.5kW continuous AC output for a house that is averaging 2 kW per hour per day. Yes, they have two EVs, but also these do not need to charge at their full potential if you plug them in every night. The author isn't generating enough energy from solar of their battery bank so it's pulling from the grid anyway for those loads, so a grid bypass (which EG4 supports up to 200A) means you don't need the inverter to pump out 34.5 kW to loads anyway.
The thing you keep glossing over is that the fundamental problem with a powerwall for scaling systems is that each battery bank you purchase requires you to purchase a built in inverter. The same nearly identical system from EG4 is an 18k + 15 kWh battery which costs $8k, and powerwalls cost $12k+. Thats a 50% premium to get you 185 LRA but 8 kWh less capacity. For an extra $250 you get an AC soft start and a 185 LRA is completed unnecessary and irrelevant.
> Yes, 48 amps at 240 is 11.5kw.
You keep saying these things like I don't understand the math.
> You don't know how to use an amp clamp and don't understand the American split phase power grid.
Lol. And you don't even understand that specifications ratings because they very explicitly say the amps at VAC ratings (120/240) because while it's entirely possible to reach the full potential of wattage... in real life, it's unlikely you will due to how split phase works with inverters. Inverters are rated by amps per leg because your loads on one 120v leg could be higher than the other one (unless all of your loads are 240v in which you would always be using the same amps on both legs).
So to conclude:
1. An identical system is $53k (Powerwall) versus $31k (EG4), which is still hilariously overpriced.
The only measurable differences are:
EG4 gets 6 more continuous AC amps (up to 1.44 kW more)
Powerwall gets much higher surge capacity (555A vs 195A)
EG4 gets 8 kWh more capacity
2. If you need more than 195A surge, you put a soft start in or just let the inverter bypass temporarily to grid.
3. You would never size this system with 3 inverters for someone averaging 48 kWh/day, so the author spent £7k on an additional battery and got an unnecessary inverter purchase which is now directly eating into his ROI.
Well, neither of these are relevant to my original comment. I never commented on the value prop of the original install, only that your comparison in pricing is just not accurate as one is much more capable. Yes, lots of people want 34kw of standing load, because they want to ensure the offset of their HVAC unit. Generally people getting these systems have ridiculous homes, I've worked on a home with 3 20kw diesel generators. I've worked on a home with a seperate 200 amp service just for their pool side projector TV. Just because someone's wants aren't reasonable doesn't mean they don't want it.
>There are hundreds of thousands of forums and YouTube videos from DIY who rave about EG4.
EG4 sucks to try to pry anything out of. I don't actually like Sol-Ark that much either, but they're better to deal with and a better deal. Best deal is just to get an SRNE or similar straight from the source. Again, I paid $800 for my SRNE. I could get a second and parallel it and be outperforming the EG4 for a $3,400 discount. Youtubers are youtubers, not a source of truth. All those same youtubers shill battle born, too...
>Lol. And you don't even understand that specifications ratings because they very explicitly say the amps...
I'm not the one that has conflated two 50 amp phases with a 100 amp service. That's a 50 amp service. 12kw is 12kw. I keep repeating the math because you clearly keep misunderstanding it. A small electric range is typically on a 240 50 amp circuit, incredibly common in most households, and that's a small one.
>Identical system.
How is this identical? $5K for all other labor and materials? How much you paying per foot for the Class K to parallel the batteries? What's the homerun distance on the PV? Your AHJ require metal conduit on the DC runs inside the attic? Shit, if they require a 3R lockable lever disco that's $900 right there before fuses. What you penetrating with? What racking system you using? Shingle or metal roof? If shingle you doing the labor to pull shingles and put in flashing or you hacking it up with some HUGS/RT Minis? What's your max span between mounts given the wind load? S-5!s and HUGs add up fast when you can't get away with a large span. What's your interlock method? If you're landing in the MSP are you derating the mainbreaker? You value your time so little after all that material that you're still under $5k?
Edit: Also, you're gonna be paying a whole lot for LTL on that partial pallet of panels and 14' (if you get the short stuff) racking.
The author of the post lives in the UK and averages 2kW load, a 4 kW PV system, and 45 kWh battery system. It's literally impossible for them to run a standing load of 34 kW for more than 1.5hrs without a grid tie. Why do you keep ignoring this?
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.
As far as I can tell if your battery isn't air cooled, it can go a very long way
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)
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.
However they also note more material studies are needed to understand these mechanisms better.
> they are doing that in China
Are they actually doing that at scale?
> 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...
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.
I also wonder if it's a scheme to get people through the door and then leech off them with a lifetime subscription.
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...
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
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.
I don't understand the comment. Of course they know where the batteries come from. They know everything about the battery.
In some mysterious future where swapping EV batteries during a road trip is a normal activity, then the battery packs won't be living in a vacuum -- their status can be known. Whether it is known by reading the pack's own electronics, by status reports from connected vehicles and charging stations, by direct measurement, or by some combination of these things: The status is knowable. It doesn't have to be a big ball of mystery.
How much value the marketplace finds in this health status is a different question. And this question is one that we cannot yet know the answer to -- this is not a reality that we presently live in.
We can speculate about how that potential future may be shaped, but that kind of speculation is kind of meritless since that version of the future may never actually happen (and at the present, it sure does seem very unlikely to happen any time soon).
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.
~~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.
Even if the swap station got to where it was hoped (no reservation needed, automated, drive in, swap, drive out), you'd have a choice between a ~5 minute stop at a swap station, or a ~10-20 minute stop at a charging station. The swap station is always going to be more expensive since it's inherently more complicated, so you're spending more to save a few minutes. And when you stop at the swap station you can go answer the call of nature and grab a snack while you wait. If you want to do either of those anyway, then visiting the swap station means you'll do the swap, then go do those other things, and probably not save any time at all.
Charging time just isn't that much of an issue at this point. I've been driving a Tesla for a decade at this point, with thousands of miles of road trips around the eastern US, and I've never found myself wishing for battery swap infrastructure. Newer cars charge much faster than mine does, too.
Your point that they are overpriced still stands though.
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.
This is the company that owns APC so its not like theyre new or untested. They just don't bother with brand awareness
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.
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.
Talking about the weather "in Europe" is like talking about the shoe size a family of 10 wears.
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 45°) and based on my observations of my neighbors, panels tend to shed the snow on their own eventually.
If prices for residential gear falls too much, I expect the manufacturers would just stop making it and focus on the commercial options instead.
If a datacenter installs a solar array + a giant battery pack for their power, that's much better than them heavily relying on a natural gas plant to generate power when the lights are out.
Why not commercial demand creates the economies of scale that bring the residential stuff down in price with them?
The reality is that many battery factories might be operating at 40-50% capacity only. Exact figures are hard to come by but there are lots of warnings about over production, surpluses, etc.. That spells a lot of trouble for some of the newer battery producers promising more efficient batteries. Because unless they price match, they price themselves out of the market almost immediately.
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.
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.
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.
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.
(Their motor inverters are world-class, but totally different topology)
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.
What I'm describing is using the cars DC charge port and connecting it to inverters DC battery port.
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. :-)
https://www.docanpower.com/panda-52v-942ah-48kwh-prebuilt-pa...
They are cheap and they work but they're not UL listed...so they dont go anywhere near my home.
The ROI is really attractive once you look past the overpriced kit.
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... :)
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! :)
Willing and allowed. In some countries it can only be done by certified electricians.
You can't and you will lose in court.
I'm pretty sure there is a clause, which states that you have to inform if you have and/or are not allowed to have fire loads, or anything that could cause a fire, or make it worse, or something along the lines in legalese. These formulations are always there because of people hoarding fuel in the basement, for example, or O2 Tank, or whatever. They are formulated in the most generic way possible to catch anything you do "wrong". Failing to follow such clauses, also when not explicitly stated, is dropping your obligations in the contract. And then there will be a clause that of course says, that not following the contract from your side, also exempts the company of paying.
Note also there are clauses that are very softly specified, like "use rooms for the intended purpose" which may be a problem if you store idk, paint in the garage, which may be flammable, in which case a fire in the garage will not be (at least fully) covered.
Ask me how I know...
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.
I got the "trick" recommended to do the things yourself, then call a certified guy, and say "look, I contracted a guy, I had no idea, he came did everything, but I got a bad vibe, I would like you check the whole installation". But it also does not really work, they will come with a contract, where you are enforced to contract them to correct any findings. And boy they will find things then...
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]
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...)
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.
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.
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.
It’s been crazy seeing the western home storage market selling systems with the €/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...
Then bought a 16kwh battery for ~£1500, 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.
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.
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.
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?
"Another way to look at this is that the investment is returning ~9%/year."
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.
You reminded me: David Roberts' often states that a hurdle for electrification and decarbonization projects is connecting them to "slow capital". Stuff like residential, community, solar, battery, heat pumps, appliances, ground source heat, yadda yadda.
I gather that there's plenty of "slow capital" perfectly happy with low risk long term modest returns. But these projects are too small to be worth the effort. Probably something about transaction costs.
My impression is there's an opportunity to bundle up these projects for the larger/largest investors. Biden's IRA created a "green bank" (RIP); maybe that was its intended function.
You're smart about money and finance, so you can probably explain what Roberts is talking about (to noobs like me).
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 £1000, because I hadn't bird-proofed underneath them (wasn't suggested by original installer). So watch out for that one.
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.
[edit: yes, I assume you also get batteries, I know that solar alone doesn't magically power your house.]
"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...
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.
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.
I installed 2800Wp solar for about €2800 ($3000, payback in: 4-5 years), and a 5kWh battery for €1200 ($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.
In my country I've never had to deal with more than 15 minutes, twice in my life. In other countries its sometimes been a day but really I just go on with my life.
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.
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
> 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.
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.
Maybe, but that power is typically generated far from where it's consumed and so you have significant transmission losses.
Not for everyone, but definitely for homeowners with suitable roofs and local utilities.
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.
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.
LiFePO4 generally degrades to 80% capacity after 10 years, that's it. Safety isn't an issue.
That probably explains it.
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.
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.
thus perhaps leading to more global warming
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.
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.
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?
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.
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.
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
Yay for New Zealand housing.
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.
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'
I don't see see a heat pump as complex. It's a compressor, valves and coils. The complexity are the stupid computers foisted onto us.
> I forgot this is an american centric forum and things are just made cheap/disposable because "it's cheaper'
We don't have a choice. Do you? We're all at the mercy of the manufactures.
Some of this extra is certainly my 6kw homelab + HVAC for that. ;)
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.
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.
In my house I only run LED lighting and an occasional oven, some phones and laptops, a cycling fridge and two weekly wash cycles, in other words, virtually no electricity. I'm at like 2 kWh per day.
The ~45 kWh a day for this family is gigantic compared to mine, like >20 of my homes in one.
But I don't have an electric car, nor electric heating or cooling, nor an electric stove.
If you have say a standard electric car like a Peugeot 208 which uses 15 kWh per 100km, and you both drive one hour (say 60km) to work and back, five days a week, that's already 25 kWh per day.
My heating bill (gas, europe) is an order of magnitude of my electric bill. Even if I'd electrify it (cheaper), it'd likely be an additional 10 kWh per day.
If you have slightly more fancy lifestyle (they run home-servers and a hottub for example), you can easily get to 45 kWh.
I think the fair comparison is to look at a household total energy expenditure (energy & $). My household has a low electrical share, theirs has an almost exclusive electrical share.
- Base electricity: 17 kWh/day (10 in months without AC)
- Heating (currently gas): 33 kWh/day
- Heating (if I switched to heat pump with COP 3): 10 kWh/day
- EV charging at 10k miles/yr: 9 kWh/day
Total if I was fully electrified: 36 kWh/day, or 13 MWh/yr
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.
That's my reasoning my new build house with plenty of land. In other scenarios it might be more beneficial to go for them.
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
They're also technically simpler and have fewer components that can wear out. And they're a single system that works both for cooling and heating, rather than needing multiple system investments.
The majority of experts believe that its the future technology stack to manage heat, not a gimmick at all.
That having been said, always start with good insulation first.
I do think more people should consider mini-split reversible AC in the UK, but the subsidy system specifically excludes it.
https://www.gov.uk/government/news/discounts-for-families-to...
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
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
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.
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 1000€ and 300€ to 500€ 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.
I am, and I am not an american, lol.
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 HeatingWe still have an ICE car and gas central heating but our combined electricity and gas bill is around £140 / month
Plan to go to EV and heat pump in our next house though
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 :(
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.
http://solarunitedneighbors.org/ | https://solarunitedneighbors.org/locations/
Which do you think is cheaper: installing an acre of solar panels across 300 seperate homes, or an acre of panels in one go on a solar farm?
I’ll take free $500 all day long please.
Depending on when you signed up for NEM you may have a guaranteed floor like 4¢/kWh or even much more.
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.
You can buy a BYD HVM 22.1 kWh for 6000 euros now (£5200) vs powerwall 2 13.5kwh for 7000 euros.
(Yes, yes: insert Musk related joke here.)
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.
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.
Pure grid cycling is also frowned on by some utilities.
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.
Utilities normally consider disincentivizing this type of behavior from residential customers as one of the factors when setting their export pricing.
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.
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?
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!
Just looking at Havenwise (https://www.havenwise.co.uk/) and my manufacturer isn't supported.
Octopus also have more flexible battery export tariffs if you want to explore those: https://octopus.energy/smart/flux/
But very often these will roughly cancel each other out.
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.
There will at least be a lag.
https://www.energystar.gov/about/federal-tax-credits/battery...
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.
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.
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.
I really need a solar solution but I feel so far out of my wheelhouse.
Solar tracking trees seem to be an interesting way to get wintertime solar way up.
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.
The article isn’t claiming this setup is universally optimal, just showing what’s possible when those pieces are combined and used deliberately.
UK off-peak energy is mostly surplus of wind, while the peak is burning natural gas. Feeding off-peak energy back to the grid at peak times makes it greener.
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.
As for your other point of becoming obsolete, why care about chasing latest fads for home appliances.
I particularly love when they are telling me that my 11 year old Prius' batteries will only last 5 years before they are junk.
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.
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.
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
Tldr; their full costs of the system are returned in 11 years.
Whether that's good depends on your perspective and assumptions, you can take a look at opportunity costs.
Imagine you have 100k for say 30 years, and you have three choices: 1. put it in a UK government bond at 4.4% -> 100 * 1.044^30 = 363k 2. put it in the S&P500 (dividend reinvested) at nominal 10% rate -> 1.7 million 3. buy a system that can't be made liquid after 30 years, but returns 11k flat per year = 330k.
1 is very safe and virtually guaranteed. 2 is considered less safe, but over 30 years broad based stock indexes are far less risky than short-term stock investing.
3 is perhaps the most difficult to make assumptions, as its house-tied and operational. Switch houses for any personal reasons, and you'll not be able to fully make your investment liquid and recuperate it. Blow an inverter, see panels degrade and replacement costs must be factored in. This pushes down the final cash position of 330k.
We could be generous and say that the 11k flat savings will increase, as electricity prices rise. Prices grew by 5% yearly in the UK, under that rate so the 11k savings today would grow to 47k annual savings in year 30, and total savings over 30 years would be 870k, pushing up the final cash position, but still not getting close to a long-term stock index investment.
But even that's somewhat generous for two reasons: one is that the 5% inflation was unnaturally high due to the EU's energy crisis from the Russian invasion, and not necessarily indicative of the next 30 years. Various countries in the EU are also curtailing renewable production because there's too much of it (precisely during the moments solar systems were making their biggest profits < 2020, you since see curtailment growing), and with more storage coming online rapidly the profits from their battery system are expected to decline, not increase. -- generally speaking, solar energy producers were more profitable a few years ago, and are becoming less and less profitable over time as competition from cheap panels undercuts them. Many countries have begun to cut the reward from exporting back to the grid from the retail prices of €0.30 to the puny wholesale prices of €0.05 and all countries are expected to go down this road eventually.
On the other hand, AI seems likely to push electricity prices higher for a long time... but it's the newest and biggest question mark compared to the other assumptions we've made above.
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?
[0] https://www.britishgas.co.uk/energy/guides/average-bill.html
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.
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
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.
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.
> 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.
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.
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!
Regarding California; you are right. I was misinformed. I would say that the grid is still very, very vulnerable due to the huge reliance on solar and overproduction during midday. That's why these examples of "I exported power to the grid" is not very interesting.
Most grids aren't built that way anyway. The residential units are sinks, not sources. In Sweden we don't even have much solar power but already there have been policies aimed at reducing grid exports from residential units, because they are mostly redundant and even harmful.
> For lithium, near-term markets appear well-supplied, but rapidly growing demand is expected to push the market into deficit by the 2030s
We've been pushed into lithium supply deficit in the past, and quickly got out of it. This is not a statement that there's not enough lithium or copper, rather that the market wants more than they currently see in development. The IEA document doesn't say anything about electrification not being possible, it's meant as a signal to policy makers to ensure that new copper mines can open up in the future, and that there's great opportunity for countries that do that.
When people are making 100 billion dollar bets on factories that use copper as an input, they are also ensuring their supply years out, which enables development of the necessary mines.
Say the worst case predictions from the document come true: there's a price spike in copper due to there being greater demand than supply. That drives up prices, which spurs on more copper mine development, but the existing copper is still being used to make the energy transition. The electrification trend continues, but just at the rate of current copper extraction! Clever people find substitutions for the electrification challenge. Or people substitute inferior and more expensive non-electrified traditional industry rather than the new tech.
There's a fundamental difference between metals for infrastructure and fuels like oil: if you have a fuel supply shortage it causes inflation, economic contraction, etc. With a shortage of copper and increase in prices in devices that use it, people wait a bit to replace that old appliance (maybe), or use an alternative that perhaps requires fossil fuels.
> Most grids aren't built that way anyway. The residential units are sinks, not sources. In Sweden we don't even have much solar power but already there have been policies aimed at reducing grid exports from residential units, because they are mostly redundant and even harmful.
Grid engineers are extremely conservative, and don't want to learn anything new, and always resist at first. Until somebody shows them how it works, they claim it's impossible. That allowing individual homes to feed back to neighbors will break everything. Then people do it and its fine. Then grid engineers claim that at 1-2% of variable supply the whole grid will come down. Then 1-2% of supply is variable solar and everything is great, so the engineers claim that 5% is the new limit. Or 10%. Or 30%. They are living in the past, don't want to learn anything new, and assume that anything new is impossible. It's a natural feeling for engineers that should be very conservative, but also incorrect. They complain about needing inertia, reactive power, without realizing that all that is quite possible with existing tech! Until a proper cost analysis is done by independent people that are fully honest about the costs, I wouldn't trust anybody saying that allowing a home to feed back into the grid is harmful. Plus, batteries negate the need to feed back into the grid at all. Keep homes as 100% sinks, just pulling down electricity far less. Or put batteries in homes to reduce their peak draw from the grid, so that all the rest of the grid can be far cheaper. There's so much potential that gets ignored just because batteries are new tech.
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.
Still, I think the grid is very vulnerable with that amount of weather-based energy. If there can be enough batteries to sink all that power generated and have it during evening til morning then that's great.
Perhaps that _can_ work in California, I really don't know what an acceptable level of storage would be. That is, how many days worth of battery power you'd want in case of bad weather conditions.
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.
I consider 2 weeks of supply a bare minimum.
That's why you're investigating hydro storage:
https://www.ess-news.com/2025/02/11/fortum-explores-new-pump...