Does a standalone battery actually pay back?

The short answer

Sometimes. A battery with no panels earns in exactly one way: it buys electricity when it is cheap and gives it back when it is expensive. Against an 8p overnight window and the 26.11p capped average unit rate, that is worth about 17p on every unit the battery delivers, and a 10 kWh system fitted for around £5,000 pays for itself in roughly ten years. On a standard Economy 7 night rate averaging 15.43p, the same battery keeps about 9p a unit and takes over eighteen years. The hardware is identical in both cases. The tariff is what decides it.

What changes when there are no panels

• Nothing arrives free. With solar, the battery stores electricity that cost nothing to make. Without it, every stored unit was bought, so the return is only ever the gap between two prices.
• It will be AC coupled. With no array to share a hybrid inverter with, a standalone battery brings its own inverter and connects on the AC side. That costs roughly two percentage points of round trip efficiency against a DC coupled setup, and it means the battery bolts on to a house rather than to a roof.
• There is no export income. The Smart Export Guarantee pays for electricity you generated. With no generation there is nothing to claim, and electricity bought from the grid and pushed back out sits outside the obligation entirely.
• Winter stops being the weak point. The usual seasonal collapse in generation does not apply, because the battery fills at the same price in January as in June. A battery only system is the most consistent version of this technology across a year.
• Roof suitability stops mattering. Heavy shading, a north facing slope, a listed building or a flat with no roof rights all rule out panels. None of them rule out a battery.

The spread depends on your overnight rate

Our arithmetic. Each off peak rate is divided by a 90 per cent round trip efficiency, the pessimistic end of the 8 to 10 per cent loss range published for AC coupled batteries, which is how a battery without solar is always wired. The 26.11p figure is the Ofgem capped average unit rate for 1 July to 30 September 2026 and varies by region and payment method. Three hundred full cycles a year is a working assumption rather than a promise.

The rates that make the top row work are electric vehicle products. Intelligent Octopus Go quotes from 8p per kWh with a guaranteed window of roughly 23:30 to 05:30, applied to the whole house including a battery, and E.ON Next Drive Smart quotes 8p from midnight to 6am on the same whole home basis. Both require a compatible vehicle or charger. Octopus Go runs 00:30 to 05:30 and does not require a home charger, but its rate depends on postcode and is not published as a single national figure, so it has to be checked against your own address. All of them need a smart meter with half hourly readings. Our tariff guidance carries the date each rate was checked, our EV charging guide covers what fitting a charger involves if that is what opens the cheaper tier, and the county pages under our coverage area carry local calculators that run this arithmetic on regional rates instead of a national average.

What it costs, and when it pays back

Installed cost bands are published UK standalone battery prices for 2026. Savings are our arithmetic at 300 full cycles a year on the per unit figures in the table above. The payback column uses the top of each cost band with the best available rate, so it is the optimistic case; on the Economy 7 column every payback figure roughly doubles. The 13.5 kWh row buys resilience as well as savings, which is why its payback reads worse than the row above it.

Two things sit behind those bands. Installed battery cost runs at roughly £400 to £900 per kWh in 2026, and a large share of the bill does not scale with capacity at all: the electrician's day, the isolators and cabling, the meter work and the network paperwork cost much the same whether the box on the wall holds 5 kWh or 10. That is why the 5.8 kWh row pays back more slowly than the 10 kWh row despite costing less to buy. Battery storage also carries 0 per cent VAT until 31 March 2027, and that relief has covered standalone batteries with no solar since 1 February 2024, worth roughly £225 to £500 against the 5 per cent rate that returns on 1 April 2027. Our battery storage guide covers the capacity and backup side of the same decision, and the full pence by pence workings sit in our guide to off peak arbitrage.

When a battery on its own works

• The roof is out. Shading, orientation, a conservation area, a listed building, or a flat with no roof rights. If panels are not happening, the battery is the only route to a cheaper unit rate.
• You already qualify for an 8p window. An electric car on the drive changes the arithmetic more than any battery specification does, because the cheap rate then applies to the whole house during the window.
• Your evening and overnight usage is high. The Ofgem high user band for 2026 is 3,800 kWh a year, about 10.4 kWh a day. A battery only earns on units it actually delivers, so heavy usage outside the cheap window is what fills the return.
• Power cuts are a real problem where you live. Rural networks, home working and medical equipment are all reasons to buy backup first and treat the savings as a bonus. That needs a gateway or an EPS circuit, not just a battery.
• Solar is a later phase. An AC coupled battery does not lock you out of adding panels afterwards, and it earns in the meantime rather than waiting for a roof budget.

When it does not

• Economy 7 is your ceiling. On an average night rate the return per unit falls by roughly half and the payback runs past every warranty on the market.
• You do not use much electricity. The Ofgem low user band is 1,600 kWh a year, about 4.4 kWh a day. A battery that never delivers more than four units a day cannot outrun the fixed cost of its own installation.
• You are buying small to keep the price down. At £3,500 to £4,500 for 5.8 kWh, the non scaling parts of the job dominate the bill and the payback is worse than the larger option.
• The plan is to charge cheap and export high. Grid charged electricity is not covered by the Smart Export Guarantee obligation. Suppliers may choose to pay for it and some do, but they are not required to, and the terms differ by tariff.
• There is no smart meter and no route to one. Every time of use tariff depends on half hourly metering. Without it there is no cheap window, and without a cheap window there is no case at all.

Paperwork, meters and one deadline

Rates and scheme rules checked against Ofgem, supplier and industry VAT guidance on 3 August 2026. The October price cap is due to be published by 26 August 2026, and every figure keyed to 26.11p moves with it. Clearline is an independent guidance service: we do not sell or fit equipment, and installations are carried out by an MCS-certified installation team for your area. If you want a second opinion on a quote you already hold, our help section covers what to check.