Headline pricing
A 5 kWh battery typically costs £3,500-£5,000 fitted. 10 kWh runs £5,500-£8,500. 13-15 kWh sits at £7,500-£11,000. Premium brands (Tesla Powerwall 3, GivEnergy All-in-One) sit at the upper end of those ranges and include their own integrated inverter, which simplifies the install.
Which brand?
There is no single best brand — they trade off price, warranty, depth-of-discharge, round-trip efficiency, EPS / backup capability and installer support. Our installers default to GivEnergy AIO, Fox ESS ECS, Solax T-BAT, Tesla Powerwall 3 or Pylontech depending on which fits your goals.
Sizing
A battery should be sized to your evening / overnight consumption, not your solar generation. Most homes do best with 5-10 kWh; EV charging households benefit from 10-15 kWh; heat-pump households often want 15-20 kWh.
Payback by capacity
On a typical Surrey or Hampshire home importing at 28p/kWh, a 5 kWh battery saves around £350-£450/year (payback 8-11 years), a 10 kWh battery £550-£800/year (8-10 years), and a 15 kWh battery £700-£950/year (9-12 years). Returns flatten beyond 10-12 kWh because most homes simply can't usefully cycle a bigger battery every day in winter.
Time-of-use tariffs change the picture. On Octopus Flux or Intelligent Go, even households with low daytime consumption can fully cycle a 10 kWh battery from cheap overnight grid power — pushing annual savings up by another £150-£300.
Warranty and lifetime
Expect 10-year warranties as standard, often with a cycle-count cap (e.g. 6,000 cycles or 80% retained capacity, whichever comes first). One full cycle per day for ten years is 3,650 cycles, so cycle limits rarely bind on residential use. Tesla and GivEnergy both offer extended warranties to 15 years for a one-off fee at install.
Real-world lifetimes on lithium iron phosphate (LFP) chemistry — used by GivEnergy, Fox ESS, Pylontech and most current Tesla units — are widely expected to exceed 15 years on typical residential cycling. The economic life often outlasts the warranty by several years.
AC-coupled vs DC-coupled vs hybrid
DC-coupled (hybrid inverter): most efficient, simpler to install with new solar. Best for new installs.
AC-coupled: battery has its own inverter, attaches to your existing AC wiring. Best for retrofits to existing solar, or where you need to keep the original solar inverter.
All-in-one units (Powerwall 3, GivEnergy AIO): integrate battery, inverter and management in one cabinet. Cleanest aesthetic, simplest commissioning, slightly more expensive headline price.
Common over-spending traps
Buying capacity 'for the future' that you won't use today: the payback period stretches every year you under-cycle. Better to install for current needs and add modular capacity later (Fox ESS and Pylontech both make this easy).
Paying for whole-home backup when EPS (essential circuits only) would do: whole-home backup costs an extra £600-£1,500 in gateway hardware and only matters if you actually experience regular outages.