What will people do at night?
ROI for 24/7 solar+battery is negative in almost all residential cases using current technology and prices.
The difference between off-peak and on-peak rates there is about $0.21/kWh in the summer and $0.29/kWh in the winter, so assume an average delta of $0.25/kWh.
Assuming no solar panels, if you charge the battery on the grid at off-peak rates and discharge it completely at on-peak rates, you break even after using about 3200kWh. Assuming 2 kWh used every day during peak rates that's a breakeven period of 4.38 years.
Maybe my calculations are wrong somewhere, and I'd love to learn if that's the case.
I also acknowledge some big assumptions: namely, that you will always need to use all your stored energy day at the peak time (reasonable in the summer when the AC is running) and that you can use all your battery power for those loads instead of grid power. On the other hand electricity rates tend to go up over time and batteries last for years.
But rates will likely increase. So will the delta between off-peak and on-peak rates. I think the true payback period is between 5 and 8 years.
Enough to keep the lights on, a fan or charging a phone. Not to run an AC or dishwasher but enough for the basics.
Think a bandwidth of 50-80$ per kwh cost levels for the manufacturer with a margin on top in a market where there's over production and prices are still trending down and margins are probably under quite a bit of pressure. That's the widely publicized cost levels for Chinese manufacturers that dominate the world supply currently. Some of the sodium ion batteries that are coming to market now are already at the lower end of that price bandwidth and could go to 10-20$/kwh over the next 5-10 years; maybe faster.
At those prices, anyone can afford plenty of battery to survive the sun not shining for days/weeks. Which in places like Pakistan would be redundant. It's far south and you can count the number of days that you shouldn't be wearing sunglasses outside per year on the fingers of one hand. Even when it's cloudy, there's plenty of light filtering through in that part of the world..
Prices you might be seeing in the US tell you more about the local politics there than the economics of batteries. The US has it self to blame for bad economics like that. Places like Pakistan aren't going to slow down because the US can't figure out all this new stuff. For them this is economic growth unlocked by vastly more energy than they've ever had access to. All they'll ever need basically.
ROI for 24/7 solar+battery is negative in almost all residential cases using current technology and prices.
This is quite cheap compared to (say) the fully loaded cost of energy from a nuclear power plant.
Smaller units will be more expensive per kWh, but not so enormously so as to render them impractical. And they will get cheaper quickly like all electronics do.
ROI for 24/7 solar+battery is negative in almost all residential cases using current technology and prices.
I can confirm that prismatic 1kWh LFP cells cost ~$60 in single digit numbers.
Granted this includes a government rebate for the battery, but overall the prices have plummeted. Any government that isn't pushing for renewables and energy storage at this point is actively working against it's citizens.
It's a fantastic way to solve oversupply; give it to everyone, including those who have batteries in areas where the weather restricts solar output.
https://www.abc.net.au/news/2025-11-03/energy-retailers-offe...