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Home Battery Payback Calculator UK (No Solar)
Standalone home battery payback for UK households on Octopus Flux, Cosy or Go — the arbitrage maths without solar. Tariff presets, capacity sizing, 10-year net.
Interactive home battery payback calculator
Worked example
A typical 10 kWh home battery on Octopus Flux (38p peak / 12p cheap), £5,500 turnkey install, household uses 3,500 kWh/yr with ~60% in peak hours:
- Annual saving
- £518
- Energy shifted per year
- 2100 kWh
- Payback
- 10.6 yrs
- 10-year net
- £-320
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Battery doesn't pay back? Try a TOU tariff first
On a flat tariff a battery saves nothing. Octopus Cosy or Flux open up the spread that makes the maths work.
Compare Cosy vs Flux →When does a standalone battery actually pay back?
The economics work when there's a wide gap between your peak and off-peak unit rates. On a flat tariff, a battery saves you almost nothing — there's no arbitrage to capture. On Octopus Flux (38p peak, 12p cheap), the per-kWh spread is 26p, which over ~330 cycles a year against a 10 kWh battery delivers around £700/yr of saving. That puts payback in the 7–9 year window for a typical £5,500 install.
The biggest mistake people make is over-sizing. If your household only uses ~6 kWh during peak hours, a 10 kWh battery is wasted capacity — most cycles, you'll discharge less than half. A 5 kWh battery costing £3,000 will hit similar annual savings with a much shorter payback. The calculator flags when capacity is bottle-necked by your actual peak usage.
What v1 doesn't model
- Solar self-consumption. If you also have solar, the maths is very different — see our solar + battery + EV combined calculator .
- Demand Flexibility Service / grid services. Octopus Saving Sessions and similar pay £/kWh for export during stress events. Add £30–80/yr for an active participant.
- Backup-power value. Some householders genuinely value blackout protection. Hard to quantify, real for some.
- Battery degradation. Capacity drops ~2%/year. We use a flat 10-year horizon.
Frequently asked questions
- Why does the calculator default to a 10-year lifetime?
- Most UK home batteries (LiFePO4 chemistry) come with a 10-year warranty and lose around 20% of usable capacity over that period. Real life can be longer, but financially modelling beyond the warranty is speculative. If your installer offers a 12-year warranty, override the figure.
- Can I make a battery pay back without solar?
- Yes — but only on a TOU tariff with a wide peak-to-cheap spread. Octopus Flux (38p peak / 12p cheap = 26p spread) is the cleanest example. On the Ofgem flat cap (27p), there's no arbitrage and the battery saves you nothing. See our [Cosy vs Flux comparator to find the right pairing.
- Is a 10 kWh battery the right size?
- For most UK homes, 5–7 kWh is plenty. The mistake people make is sizing for total daily consumption rather than peak-window consumption — the actual quantity you can shift each day. The calculator flags when your battery is bigger than your peak use, in which case a smaller (cheaper) battery would save almost as much.
- What about pairing with solar?
- Different maths entirely. With solar, the battery captures unused generation rather than buying cheap-rate kWh — see our full [solar + battery + EV combined calculator. Solar economics dominate the equation; this calculator is for households without PV.
- Are home batteries ECO4 or BUS-grant-eligible?
- Not currently. The Boiler Upgrade Scheme covers heat pumps only. ECO4 covers fabric-first measures and heating, not standalone batteries. Some councils have limited local battery grant schemes — check your authority directly. The lack of grants is the biggest reason payback timeframes are 7–10 years rather than 4–6.
Pairing batteries with the right tariff
Batteries only earn their keep on a TOU tariff with a wide peak/off-peak spread. The cleanest comparison: Cosy vs Flux side-by-side , or for the dynamic version, Octopus Agile . If you also have solar, the UK SEG export tariff comparator shows which supplier pays best for your exported kWh — which compounds with battery savings.
Related calculators
Ranked by topic overlap with this tool.
- Solar Panel Savings Calculator UK — Full scenario comparison with battery modelling, SEG export income and 25-year stress tests.
- Solar + Battery + EV Combined Savings Calculator UK — Combined savings from solar + battery + EV charging — compounding interactions, 15-year payback on the whole stack.
- Solar Export Tariff Comparator UK — Compare UK SEG tariffs side-by-side — Octopus, E.ON, British Gas, EDF and more. See exactly what each pays for your export kWh.
- Octopus Cosy vs Flux Tariff Comparator UK — Side-by-side comparison of Octopus Cosy (heat-pump-tuned), Flux (battery-tuned) and the standard variable. Annual £, peak-window share, export income.
- Solar Payback by Postcode UK — Simpler postcode-first variant with regional samples for major UK cities.