Is a home battery worth it?
A battery does not make electricity. It buys it when it is cheap and sells it back to you when it is dear. Whether that pays depends entirely on the gap between those two prices.
300 is close to daily
£505 a year against roughly £7,000 installed, shifting 2,640 kWh from peak to off-peak. Most batteries are warrantied around 10 years, so that is a long wait.
The uncomfortable truth about batteries
On a standard tariff, a battery rarely pays for itself within its warranty. It needs a time-of-use tariff with a genuinely cheap overnight rate to work — and it needs you to actually cycle it most days. A battery cycled 150 times a year takes twice as long to pay back as one cycled 300 times.
Batteries make far more sense alongside solar, where they lift how much of your own generation you use from around 50% to 75% or more, or alongside an EV and heat pump that give you somewhere to put cheap overnight power.