Stage 4 of 8
Do you actually need a battery?
A framework that walks you through how tariff, daytime usage, and EV ownership shift the answer.
The honest answer to “do I need a battery?” is “it depends” — and the things it depends on are the same five things the framework below asks about. Fill it in and you'll see a weighted view, not a yes/no.
A few things worth knowing up-front:
- Battery costs are typically £4,000-£7,000 for an 8-10 kWh mid-market system installed (Tesla Powerwall sits at the higher end; GivEnergy / Powervault mid-range).
- Battery warranties are typically 10 years, which is your payback ceiling — anything longer than 10-year payback eats into uncovered years.
- Backup capability is not standard — many batteries can't run during a power cut without an extra “EPS” (Emergency Power Supply) module.
- You can usually add a battery later if you decide it's worth it — most modern inverters support retrofit.
One number is worth visualising before the framework: where your generated electricity actually goes. Without a battery, most homes export 55-80% of generation at low export rates. A battery flips that ratio.
A battery pushes roughly 30-45 percentage points of generation from exported (paid at your export tariff, typically 4-15p/kWh) to used yourself (offsets imports at typically 22-28p/kWh). The bigger that gap, the more a battery is worth.