Are Home Batteries Worth It in the UK?

A battery does not generate electricity. It stores electricity for later — and loses some energy along the way.

Its financial benefit is:

The electricity purchase you avoid, minus the charging cost or export income you give up.

That second part matters. If surplus solar could earn an export payment, storing it has a cost even though you are not buying electricity from the grid.

Take an illustrative 90% round-trip efficiency: put 10kWh into storage and receive 9kWh back for use in the home.

If that 9kWh replaces electricity costing 26.32p/kWh, it avoids about £2.37 of imports.

These are alternative examples, not savings to add together. Each assumes all 9kWh returned replaces electricity you would otherwise buy at 26.32p.

The 26.32p benchmark is Ofgem’s GB-average Direct Debit default-tariff electricity rate for October–December 2026. The 7p import rate, 12p export rate and 90% efficiency are illustrative assumptions, not a tariff offer or equipment guarantee.

The same amount of stored electricity can create very different savings.

If you can buy electricity at 7p/kWh and sell surplus solar at 12p/kWh, charging the battery cheaply and exporting the solar can be financially better than storing that solar.

For the same 10kWh charging input and the same assumed losses:

• Grid charging costs 70p.
• Solar charging gives up £1.20 of export income.
• Cheap grid charging is 50p better for that amount of energy.

That assumes both options can serve the same later demand, with suitable controls, charging time and compatible tariff terms.

Solar electricity is not automatically the cheapest electricity to store. Compare what it could earn elsewhere.

The best approach can change with the weather, tariff and household routine. Compare solar storage, cheap-rate charging and a combination using the same household assumptions.

The next question is how often the opportunity actually occurs.

Using the 7p charging rate, 26.32p avoided import rate and 90% efficiency above:

These are worked examples, not forecasts. They assume every returned unit replaces a 26.32p import.

For a hypothetical £5,000 installed battery, those benefits imply simple paybacks of approximately 30, 15 and 10 years respectively.

Same purchase price. Very different investment.

Actual results depend on charging opportunities, demand, capacity, power limits and losses. These simplified figures exclude additional standby consumption, degradation, maintenance, finance and replacement costs. Tariff changes can also alter the result.

Do not accept a forecast based on a full charge and discharge every day unless your household’s usage supports it.

Suppose a quote shows:

• Solar alone: £700 annual benefit.
• Solar plus battery: £950 annual benefit.

The battery adds £250, not £950.

Compare that £250 with the additional installed cost of adding the battery, using otherwise comparable systems and assumptions.

If the battery costs an extra £5,000, simple payback is 20 years. We would challenge that as a savings-led purchase and test a cheaper or smaller option.

A combined package can look attractive while the battery itself adds relatively little. Ask for both comparisons.

A larger battery needs more useful work to justify its extra cost.

Suppose the next size up costs another £2,000 but adds only £100 a year of savings. That additional capacity has a 20-year simple payback, even if the smaller battery makes good financial sense.

Judge the extra capacity by the extra saving.

Check both:

• Usable capacity, in kWh: how much energy is available after any reserve.
• Charge and discharge power, in kW: how quickly the system can store or supply electricity.

A battery can hold enough energy for an evening and still need grid support when several powerful appliances run together.

Count the demand that the home battery can usefully serve.

If your EV can charge directly during the same cheap overnight period, routing that electricity through a home battery first adds storage losses. Do not count all the car’s annual charging as expensive demand the home battery will replace.

A heat pump may create more demand outside cheap hours, which can strengthen the opportunity. But winter usage, charging windows and battery power still limit what can be shifted.

A battery changes when electricity is bought. It does not improve the heat pump’s underlying efficiency or turn summer solar into a winter energy supply.

Ask for:

• The complete installed price, including inverter and necessary electrical work.
• Usable capacity after your chosen reserve, plus charging and discharge power.
• Annual savings against the same home without the battery.
• Charging costs, lost export income and losses included in those savings.
• A lower-use or less favourable tariff scenario.
• Warranty terms, retained-capacity commitments and any usage limits.
• Confirmation of exactly what works during a power cut, if backup matters to you.

Backup can be a valid reason to buy, but it is not automatic and may require additional equipment. Value it separately from bill savings.

For the equipment and installation questions, read the Battery Guide.

Where there is regular demand, a worthwhile price difference and a sensible installed cost, we would investigate seriously.

Where demand is low, export income is valuable or the proposed system is oversized, we would be prepared to choose a smaller battery or none at all.

A positive annual saving is the starting point. The purchase price, warranty and realistic working life decide whether it is enough.

A battery earns its place through what it saves each year — not how much it can hold.