No roof for panels? A battery can still cut bills by charging cheap overnight and discharging at peak prices. On the right tariff the arbitrage is real — but the VAT treatment and cycling economics need honest maths before you buy.
Time-of-use tariffs sell overnight electricity at 7–12p/kWh against peak rates of 25–35p. A 10kWh battery cycling daily shifts ~9kWh usable from cheap to peak: roughly £1.60–£2.30 saved per full winter cycle, less in summer when usage drops. Realistic annual savings for a high-consumption household: £350–£550. Smart tariffs that also pay for peak export can push this higher.
Batteries installed with solar enjoy 0% VAT. A standalone retrofit battery without solar is generally treated at 20% VAT — adding £800–£1,200 to a typical install and stretching payback by 1.5–2 years. Factor this into every quote comparison, and note the position if you might add solar later: bundling changes the tax treatment.
A 10kWh battery-only install at ~£5,500–£7,000 including 20% VAT, saving £400–£550/yr, pays back in 10–14 years against a 10–15 year warranty life — marginal on savings alone. The case strengthens with: very high evening consumption, EV charging (already on a cheap tariff), export-payment stacking, and backup-power value during outages. It weakens for low-usage households, where cycling revenue can’t cover capital.
If any solar is plausible within 2–3 years, bundling usually wins: 0% VAT on the whole package, one installation visit, and solar self-consumption stacking with tariff arbitrage. Battery-first only makes clear sense where panels are genuinely impossible — unsuitable roof, shading, leasehold restrictions. Size it with our battery sizing guide.
Facts checked 21 August 2026. We link to official sources and show when facts were last verified. If a scheme changes, we update the page.
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