Can you have a home battery without solar panels?

What a standalone battery actually does

A home battery does not need solar panels to work. It can be wired into your consumer unit so that it charges from the grid during cheap overnight hours and then discharges that stored electricity back into your home during the day, when the standard rate is higher.

This is different from a solar battery, which mainly stores free electricity generated by panels on your roof. A standalone, grid-charged battery stores electricity you have bought, just at a lower price than you would otherwise pay for daytime use.

The benefit, often called tariff arbitrage, relies entirely on there being a meaningful price difference between cheap and expensive periods on your electricity tariff.

How tariff arbitrage works, with a worked example

Suppose, purely for illustration, a household is on a time-of-use tariff with a cheap overnight rate of 15p per kWh for a seven-hour window and a daytime rate of 30p per kWh. These figures are assumptions for this example only and are not current market prices; check your own supplier’s rates.

If a battery with 5kWh of usable capacity is charged fully overnight and that stored electricity displaces 5kWh that would otherwise have been bought at the daytime rate, the saving on that one cycle is 5 × (£0.30 − £0.15) = £0.75.

Repeated every day of the year, that is illustrative only: £0.75 × 365 ≈ £274 per year, before accounting for battery efficiency losses, which typically mean only around 85 to 90% of the energy put in comes back out, and before accounting for any standing charges or daily charge limits set by your tariff.

The practical limits

The saving is capped by your usable battery capacity. A battery cannot shift more electricity than it can store in one overnight charge, so a household using far more than the battery’s capacity each day will only have part of its usage covered.

Not every tariff has a wide enough gap between cheap and expensive rates to make the arithmetic worthwhile once you include the cost of the battery and installation. It is worth running the sums with your actual tariff rates and usage pattern before committing.

Battery degradation over time, inverter losses, and the standing cost of maintaining a second piece of home electrical equipment should all be weighed against the likely annual saving.

Any figures in this guide are illustrative assumptions for explaining the principle, not a quote or guarantee of savings. Ask an installer to model your actual tariff and usage.

When a standalone battery tends to make more sense

Standalone batteries are most commonly considered by households already on, or planning to move to, a time-of-use tariff with a large day/night price gap, or those wanting backup power during outages as a secondary benefit.

If you are also considering solar panels, it is usually more cost-effective to size the battery alongside the solar system from the outset rather than installing a standalone unit first and adding panels later, since the inverter and wiring requirements can differ.