The calculator
Battery payback calculator
See what a home battery could save you at 2026 UK electricity rates. Enter your usage and tariff — we compare importing at peak vs charging overnight and show your annual saving, payback years and 15-year net position. All assumptions are editable below.
Your home
Annual electricity usage
Current tariff
Do you have solar panels?
Battery size
£561
vs staying on your current import rate
14.4 yrs
Install cost £7,000 · 0% VAT
10 kWh
Offsets ~8.6 kWh/day peak import
£234
After install cost, degradation & cycles
15-year cumulative net position
Line crosses £0 at payback.
Typical fitted price
£6,000 – £8,000
Typical fitted range for a 10 kWh system with 0% VAT — exact price depends on your home (inverter needed, cable runs, G99 approval, roof access). See our finance and £0-upfront options guide if you don't want to pay it all up front.
Ready for real quotes?
Our calculator uses averages. An MCS-certified installer will spec the exact battery, inverter and G99 approval for your home — and give you a firm fitted price with 0% VAT.
Get exact quotes from MCS-certified installersOur assumptions (edit any of these)
Peak import rate (p/kWh)
Off-peak charging rate (p/kWh)
Fitted install cost (£)
- · Round-trip efficiency: 90%
- · Cycles per year: 340 (near-daily use)
- · Annual capacity degradation: 2% (floor 70%)
- · Solar uplift when present: +10%
- · 0% VAT applied to fitted install cost (relief runs until 31 March 2027).
- · Standing charges excluded — they apply regardless of battery.
This is a modelling tool, not a quote. For an exact figure use the installer quote form.
FAQ
Quick answers about battery payback
Is a battery worth it without solar?+
Yes on a smart tariff — the ~20p/kWh gap between overnight and peak is the payback engine. See our guide on home battery storage without solar.
What size battery do most UK homes need?+
A 3-4 bed home usually lands between 10 and 13.5 kWh usable. Larger only helps if your evening/night draw is above ~15 kWh.
Does the 0% VAT really apply?+
Yes — 0% VAT on a fitted battery install runs until 31 March 2027 under HMRC's energy-saving materials relief.
How long do the batteries last?+
Most credible warranties cover 10 years and 6,000+ cycles to 70% capacity. That's roughly 15 years at daily use.
Can I finance it instead of paying up front?+
Yes — installer finance, subscription and mortgage advances all exist. Our finance guide runs the honest trade-offs.
How we calculate
Method, in one paragraph
We take your annual usage, estimate the share shiftable into an overnight off-peak window (capped by battery size and round-trip efficiency), then value that shift at (peak − off-peak). Solar adds a modest free-charging uplift. Payback = install cost ÷ annual saving; 15-year net applies published degradation curves. All numbers are editable — nothing is hidden.