Battery prices, sizing logic, and an honest take on when home storage pays back — and when it doesn't.
Fitted prices for the most common UK home batteries in 2026:
The rule of thumb: size the battery to your evening consumption, not your full daily use. A typical 3-bed semi uses 8–12 kWh per day, but only 3–5 kWh of that lands between 5pm and 10pm when the panels aren't producing.
A 5 kWh battery covers most evenings for a small household. A 10 kWh battery covers a family with an EV charging overnight. Anything bigger usually means you're trying to make the battery do something it isn't good at — like full off-grid living.
A battery saves you the spread between the import rate (~28p/kWh) and the export rate (4–27p/kWh depending on SEG tariff). On a basic SEG tariff, that spread is roughly 24p per cycled kWh. A 5 kWh battery cycling once a day saves £438/year — paying back in 7–10 years.
On a high-export tariff like Octopus Outgoing Fixed (27p/kWh), the spread shrinks to ~1p — and a battery barely pays back at all. The cleverer play on those tariffs is to skip the battery, export everything, and use Octopus Go for cheap overnight import.
Tier 1 (proven 10-year performance, well-stocked spares): Tesla, GivEnergy, Fox ESS, SolarEdge.
Tier 2 (cheaper, decent reliability, smaller installer network): Pylontech, BYD, Sunsynk.
Skip: any battery with no UK importer, no UKCA marking, or a warranty that excludes 'commercial use' but defines that term loosely. We've seen warranty claims rejected on perfectly normal residential systems.