Question 1

What size solar battery do I need?

Accepted Answer

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.

Question 2

Is a 5 kWh or 10 kWh battery better?

Accepted Answer

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.

Question 3

How much does a 10 kWh home battery cost?

Accepted Answer

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.

Question 4

Are home batteries VAT-free?

Accepted Answer

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.

Question 5

Will a solar battery work in a power cut?

Accepted Answer

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

Question 6

Can I charge a battery on a cheap overnight tariff?

Accepted Answer

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

Question 7

Is the result guaranteed?

Accepted Answer

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

Question 8

Is advertised battery capacity the same as usable capacity?

Accepted Answer

Not always. A 10 kWh nameplate does not necessarily provide 10 kWh to the home: the battery management system reserves a portion and conversion causes losses. Compare the usable kWh stated in the quote.

Question 9

Can a battery be added to an existing solar PV system?

Accepted Answer

Often yes, but the wiring and inverter choice matter. Ask whether the proposal is AC-coupled or requires an inverter change, and whether the quoted price includes metering, controls and any required electrical work.

Question 10

Which battery warranty figures matter most?

Accepted Answer

Read the years, permitted cycles or energy throughput, and the minimum retained capacity together. A long warranty period on its own says little about how much usable storage will remain.

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

What to check on a UK battery quote

Solar battery questions in the UK