A battery without solar isn't about generating power — it's about buying it cheap and spending it expensive. Modern flexible tariffs have made that a legitimate play for some households.
The math on arbitrage alone
On a tariff with a 7p overnight rate and a 30p peak rate, every kWh you shift from peak to overnight is worth 23p. A 10kWh battery, cycled once daily, shifts about 3,300 kWh/year — that's £760 of annual saving. A £5,000 battery pays back in under seven years.
Three profiles that pay back
- High evening-peak user: electric cooking, TVs, big families. Biggest daily arbitrage opportunity.
- EV owner without solar: overnight tariff already; a battery adds a second shift for the house.
- Electric heating (storage or heat pump): shifts a huge kWh-per-day load. Payback can be under five years.