Home batteries are much quicker to pay off than solar at the moment. This is largely due to being able to do strong arbitrage between import and export prices at different times of day, and some high guaranteed consumer export tariffs.

There’s no guarantee things will stay that way though, not least because the more storage added to the grid, the more those arbitrage opportunities get soaked up.

Grid scale BESS (battery energy storage system) in the UK is growing fast, because it makes financial sense. There's one that just expanded from 100MWh/100Mw to 475MWh/350MW: https://www.pacificgreen.com/energy-parks/energy-park-case-s... . It's easy to run the numbers, easier to make a payback calculator with AI. Take a look at the Anker E5000 / Ecoflow Stream 5000, and run the numbers yourself, I'd be interested to see what the payback would be for you.

> I'm highly skeptical that a battery + inverter (w/o solar), using time-of-use for payback would ever make pure financial sense.

Ever? Batteries are 10x cheaper today than they were ~a decade ago. If that trend continues for even a little longer, they'll be absolute no-brainer like solar is today within the next 5 years.

2026 seems to be roughly the break-even point. And whether it's worth it depends on where you live (greatly affects the cost of both installing a system, and buying energy from the grid).

Yeah, I bought an inverter from eBay, and a battery from AliExpress. Also signed up to axle energy to reduce payback period. Most people would need an electrician to connect it though. If you just asked an electrician for a new circuit with a simple route to an isolator, it wouldn't be expensive.

I import more than I export in December and January, but for every other month of the year it’s the reverse by some margin. My annual electricity bill is net negative, and the installation cost will be paid off in 7 years. The numbers would be even better in, say, Spain, but they are perfectly adequate here, despite suboptimal latitude.

Incidentally, the grid only knows about my exports. Self-consumption manifests as demand reduction, so UK solar production and electricity consumption is probably higher than aggregate figures suggest.

True, but if you get cheap power from solar for the rest of the year, and charge the battery from the grid off peak when there's no solar to charge, you should end up paying less than just the standard rate.