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this post was submitted on 17 Sep 2025
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Braindead strategy, that most likely is discrete fossil fuel shilling, for purposes of making decision inpractical.
The cost of storage as a baselines is how much you can charge/discharge per day. Bonus for smaller (= cheaper) that can have more discharge/charge than its capacity per day. Plus the resilience/reserve capacity value which is a convenience factor. Resilience alternatives include fire places or gas generators (that are not expected to be used often) which tend to be cheap per kw. But noise, smell, variable costs, and startup effort are all inconveniences. Driving an EV to a public charger can be a similar inconvenience level to a generator for resilience value. If a 1mwh battery is used 10kwh/day it costs 100 times more per kwh than a 10kwh battery.
OP gives an example of 12kwh summer use (no AC?) which is very high for most people, but can include cooking and floodlights.
The braindead analysis parts are "because 100 days of 10kwh surpluses happen, I need 1mwh battery". Actual battery storage requirements are the lowest theoretical winter solar production over 1-2 weeks, together with running pumps for heat (stored mostly in fall) distribution. A 10kwh/day maximum deficit for 1 week straight, with 60 day average deficit of 5kwh/day (without requiring additional heat input), means that any consideration for a large static battery should stop at 70kwh. This is sharply reduced with 1 or 2 EVs where summer surpluses are free fuel, and EV provides backcharging at 3kw whenever needed. 30kwh battery is plenty to charge an EV overnight (300km range for small car) before next day's sunlight exceeds needs. Even less battery with 2nd lightly used EV, but 30kwh will be cheaper than un-needed EV.
Instead of relying on batteries for heat generation, which is where $100k 1mwh delusion proposition comes, heat generated from solar stored in under $1/kwh hot water and dirt storage. Outside of winter, this also provides completely unlimited showers and hot tub use, and a $10-20k heat pump and heating system (fossil fuel systems often cost the same) and insulation improvements is the the unquestionable non-distracting path.
I looked into one of these thermal systems for my own place but the outlay is just massive for the 11 weeks a year I really need heat, and the rest of the year it's just a stupidly oversized hot water heater that is cooking my glycol and DC pumps.
I ended up paneling up and putting a dumb 9kw resistive boiler for my hydronic floors. The house slab is the battery and although inefficient in terms of strict energy use, winter sun on my cheap pallet of panels dumps plenty into the slab all day. I do have to light the stove if we get a snow storm for a day or two though
Yes. Hydronic flooring is cheap at construction time. Complicated if drilling into finished ceilings/floor with thicker under floor space making. But instead of 9kw of winter electricity you are forced to import, it is free fall surplus generation. 100w of pump circulation.
But you are saying, a resistive boiler made more sense than a heat pump, with the hydronic floor conversion. At first I thought you were just saying resistive heating electric floor. The latter, to me, would be the cheapest capital outlay conversion, and then a heat pump would beat a resistive boiler on operation costs if hydronic.
Did you investigate all of these alternatives?
Yeah I already had the hydronic floors and ran numbers on heating the floors off thermal solar panels, propane, heat pump, and the resistive boiler. The thermal panels made the least sense because they are useless eight months of the year.
The heat pump might have worked but when I really needed it my semi-outdoor closet would be in single digits and full of water supply pipes so the heat pump would be least efficient when I needed it most, and would not help keep the closet warm.
The resistive boiler meant I could add a bunch of panels to run it during the day and get the floors up to 85F, then run all electric appliances with no worries during the day the rest of the year with the extra capacity. So instead of being net positive generation from 10am to 4pm in summer, its now 8 am to 6pm with way more than I can use at peak.
(OP here) Sorry mate, are you accusing me of being in the pocket of Big Oil? Here's everything I've written about solar over the last decade - https://shkspr.mobi/blog/tag/solar/ - feel free to point out where I've said "yay fossil fuels!"
I didn't include AC because that's not a thing in the UK.
Oh, and I don't use electricity for primary heating. Solar thermal is pretty useless in my part of the world because you don't need much hot water in summer (mmmm! Cold showers!)
As I said in my post, this is a purely theoretical discussion about what future technology might look like. Your argument is like someone from 2001 going "a recordable CD can hold 650MB - so you only need two for a really long car trip. There's no way people in the future will have 1TB hard drives! For anything else, just use AM radio."
Basically, one of us is braindead - and I'm not so sure it is me!
Ok, to be polite, you were just mistaken in portraying a 1 mwh battery as a reasonable idea. It is just so absurdly stupid that motives for the proposal need to be looked at. I accept your admission of stupid instead of evil.
I'm sorry you didn't read my article. If you had, you would have seen me say…
And
And
At no point did I say it was a reasonable idea. I went out of my way to demonstrate how impractical it was.
I accept your admission that you didn't read my post means you are stupid rather than evil etc.
But there are sensible paths to going off grid. Why you would write about an impractical fantasy path was my puzzlement.
There's this thing that writers do called "thought experiments". It is a form of intellectual exercise to examine what happens at extremes.
It helps us explore an idea by future gazing and, yes, getting a little ridiculous. Imagine someone in 1975 saying "what would the world be like if we all had Gbps Internet?"
There was nothing of that speed available for domestic use, but thinking about an "impractical" technology means they can ask "would video conferencing disrupt the travel industry?"
That's what I'm doing. 25 years ago home solar was too expensive to be practical. 25 years ago having a 5kWh battery in your home was close to impossible.
In 25 years time will batteries be cheap enough for us each to have a MWh in the loft? I reckon so. What does the world look like when every home has the ability to be energy self-sufficient using solar?
At $20k/$30k per mwh would make 100 kwh $2-$3k. 100kwh would still be more than you need, and so it is pretty affordable now.
There are some cheap/"bad discharge rate" chemistries like iron air. They'd be too heavy for loft, but could be foundation walls or crate in your back yard. Not a technology likely to be mass produced enough, and shipping costs very high.
We were at this point in 2019. The raw materials are 1/3 the price today. 100kwh is already more than you need. Corruption of tariffs, and artificial price barriers by electric monopolies and their regulator minions inflate prices in our countries.