UK solar battery size, cost and payback calculator

⚡ Three details about your home

Annual electricity use

kWh/year

Use the total from your latest 12 months of bills or supplier account.

Solar PV system size

Still planning the array? Start with the UK solar panel calculator.

When do you use most electricity?

I have smart-meter export dataOptional

I know how much solar I exportedThis is more accurate than a general usage profile.

Calculate cost and paybackUse the editable estimate or enter a complete installed quote.

Battery system price installed

The guide price follows the selected usable capacity. Replace it with your VAT-inclusive quote.

Include confirmed fundingOnly if a grant is genuinely available to you

Refine the value of one shifted kWh

Value of each kWh discharged from the battery

£/kWh

Use the difference between the import price avoided and the export payment or credit forgone. The default is deliberately editable.

⌁ Your battery estimate

Recommended usable capacity——

Compare another capacity—

Electricity independence——

From the battery each year——

Grid imports reduced——

Suggested battery inverter—check peak loads and phases

Estimated net investment——

Annual financial benefit—from the chosen kWh value

Simple payback—battery replacement excluded

—

Energy flow

What could change after adding a battery?

The annual model shows where solar generation could go.

Estimated generation—

Without a battery

Used immediately—

Sent to the grid—

With battery —

Used immediately—

Charged into battery—

Sent to the grid—

Across the year

How much energy could the battery return each month?

Seasonal generation limits charging in winter.

Energy delivered by battery—

During a power cut

How long could essential loads run?

Choose the average load you want to support.

Approximate runtime——

Backup requires a compatible inverter, changeover equipment and a suitable essential-load circuit; a battery alone does not guarantee power during an outage.

Quick comparison

5, 10 or 15 kWh solar battery?

Compare each capacity using the same household data; the balanced option is marked automatically.

What battery size does a UK home need?

A 5 kWh battery can suit a smaller array or low evening demand. About 10 kWh is a common comparison point for larger household loads, while 15 kWh only adds value when enough surplus is available to cycle it.

The model caps domestic comparisons at 30 kWh. Larger loads need interval-data modelling rather than a household rule of thumb.

Solar battery cost and savings in the UK

The editable starting price is a planning estimate, not a quotation. Since 1 February 2024, qualifying residential electrical storage installations can be zero-rated for VAT under the temporary rules running to 31 March 2027.

Savings depend on your import tariff, SEG export rate, time-of-use charging, round-trip losses and how often the battery cycles. Do not value every stored kWh at the full retail rate if exporting it would have earned income.

Method, UK rules and limitations

Generation uses a broad UK yield of about 900 kWh per installed kW and a seasonal profile. Battery charging is limited by monthly surplus, household demand, usable capacity, cycling and 90% round-trip efficiency.

Official references: HMRC battery VAT guidance and Ofgem SEG guidance. This is not an installer design, MCS quote or DNO approval.

Solar battery questions in the UK

Straight answers before comparing home battery quotes.

What size solar battery do I need?

Start with the solar surplus available on a typical day and the electricity used after sunset. A battery that cannot be regularly charged and discharged is usually oversized.

Is a 5 kWh or 10 kWh battery better?

5 kWh may suit lower demand; 10 kWh can shift more energy and run essentials longer, but only when the PV system creates enough surplus. Compare both in the calculator.

How much does a 10 kWh home battery cost?

Prices vary with chemistry, inverter, backup hardware and installation. Enter a complete VAT-inclusive quote; the calculator’s figure is only an editable market starting point.

Are home batteries VAT-free?

Qualifying residential electrical storage installations are included in the temporary zero-rate rules from 1 February 2024 to 31 March 2027. Confirm how the rules apply to your installation and quote.

Will a solar battery work in a power cut?

Not automatically. The system needs backup-capable controls, safe isolation from the grid and enough inverter power for the selected circuits.

Can I charge a battery on a cheap overnight tariff?

Many systems can, if their controls and tariff support scheduled charging. This can change the economics, but battery losses and export rules still matter.

Is the result guaranteed?

No. It is a planning model. Weather, shading, household timing, tariffs, degradation, control settings and equipment limits change real results.

Solar battery size and payback calculator

What could change after adding a battery?

How much energy could the battery return each month?

How long could essential loads run?

5, 10 or 15 kWh solar battery?

How to size a home battery for solar panels

Start with real data

Compare usable capacity

Check power as well as kWh

Price the whole system

What battery size does a UK home need?

Solar battery cost and savings in the UK

Method, UK rules and limitations

Solar battery questions in the UK

What could change after adding a battery?

How much energy could the battery return each month?

How long could essential loads run?

5, 10 or 15 kWh solar battery?

How to size a home battery for solar panels

Start with real data

Compare usable capacity

Check power as well as kWh

Price the whole system

What battery size does a UK home need?

Solar battery cost and savings in the UK

Method, UK rules and limitations

Solar battery questions in the UK

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