Why a battery on its own can beat solar
Most solar quotes assume every unit your panels make replaces electricity at the full daytime price. Once you have a battery charging on a cheap overnight tariff, that's no longer true: your solar only replaces electricity you'd have bought cheaply anyway.
Without a battery
Solar you use saves the daytime rate, about 27p a unit.
With a battery on a cheap tariff
You already fill up at about 7p and avoid the daytime rate. The battery does the saving.
So solar is worth less
Each solar unit you use now only saves about 7.8p, not 27p.
Your numbers
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Your battery
Suggested: about 7.7 kWh covers your day outside cheap hours — compare all
Your tariff
Solar (existing or new)
Battery only
13.3% a year
≈ £562 extra saved a year on £4,210
Battery added to existing solar
5.1% a year
≈ £216 extra saved a year on £4,210
New solar + battery
7.8% a year
≈ £792 extra saved a year on £10,210
Yearly return on the money you spend
What each solar unit you use really saves (pence)
| Option | Cost | Saved a year | Return |
|---|---|---|---|
| Battery only | £4,210 | £562 | 13.3% |
| Battery added to existing solar | £4,210 | £216 | 5.1% |
| New solar + battery | £10,210 | £792 | 7.8% |
Nothing on your roof
- No scaffolding, roof drilling or planning worries
- Works for flats, shaded roofs and listed buildings
- One box, usually installed in a day
- Add solar later if you want: hybrid systems have solar inputs built in
How we worked it out
Solar makes about 900 kWh per kWp a year in the UK. We assume 50% is used at home and the rest exported. Battery savings use the same model as our savings calculator: one charge a day at the cheap rate, 90% efficiency, covering your daytime and evening use. These are estimates for illustration, not a quote or financial advice. We start the export rate at 5p, a typical payment; the best fixed export deals pay about 15p. Adding a battery to existing solar counts only the extra saving over your panels on their own, against the battery price.