Home energy guide
Home battery savings: cheap night rates and stored solar
A battery saves money two ways: buying cheap electricity at night to use in the day, and keeping your spare solar instead of exporting it. On today's prices, the night-time trick is usually worth more.
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Two ways a battery earns its keep
- Charge cheap at night, use it in the day. Each unit saves about 19.1p.
- Store spare solar instead of exporting it. Each unit saves about 13p.
See the numbers
| Use | Saves | Costs | Net per kWh |
|---|---|---|---|
| Charge at 6.5p night rate, use instead of 26.32p | 26.32p | 6.5p ÷ 0.9 = 7.2p | ≈19.1p |
| Store spare solar instead of exporting at 12p | 26.32p | 12p ÷ 0.9 = 13.3p | ≈13p |
Night rate: Intelligent Octopus Go (from 6.5p, checked 31 Oct 2026). Day rate: Ofgem cap average Oct–Dec 2026. Export: Outgoing Octopus 12p. Round-trip efficiency is our assumption.
What that adds up to
A typical 10 kWh battery saves around £512 a year. At £6,500 fitted, it takes about 13 years to pay for itself.
See the numbers
A 10 kWh battery (9.5 kWh usable) cycled from the night rate 250 times a year delivers about 2,375 kWh and saves about £454. Storing 500 kWh of spare solar adds about £58.
That's longer than many warranties (often around 10 years), so a battery on its own is rarely a quick win. It looks better when:
- it goes in with solar, sharing the scaffolding and inverter;
- your day rate is well above the cap, or you use most of your power in the evening;
- you join an export tariff that pays more at peak times, like Prime Outgoing Octopus at 16p from 4pm to 7pm. We haven't modelled that here.
The limit people miss
A battery can only replace electricity you'd otherwise buy at the higher rate. If your home uses 6 kWh between 07:00 and 23:30, a 10 kWh battery can't save more than 6 kWh a day, however big it is. Check your smart-meter data before choosing a size.
Already charging an EV on a night tariff?
The car already gets the cheap rate, so the battery only helps the rest of the house. Our guide to home battery storage and Powerwall costs in the UK looks at that case, and our EV tariff comparison covers the night rates.
Sources (checked 27 October 2026 unless stated)
- Energy Saving Trust: Solar panels: battery storage around £5,000–£8,000
- Octopus Energy: Intelligent Octopus Go: from 6.5p/kWh (checked 31 Oct 2026)
- Ofgem price cap, 1 Oct–31 Dec 2026 (published 26 Aug 2026)
- Octopus Energy: Outgoing Octopus: 12p flat; Prime Outgoing 16p (4pm–7pm) / 9p; 12 panels + 10 kWh battery £11,115 (April 2026 prices)