Home battery storage, with or without solar panels.

Can a home battery work without solar panels?

Yes. A battery on its own fills up from the grid while electricity is cheap and supplies the house from storage when the price goes up. For that you need a time-of-use tariff, with a lower rate overnight or at set times of day, and those tariffs run on a smart meter.

Whether it pays comes down to the gap between the cheap and the dear rate, and to how much power the house uses in the dear part of the day. A household that does its cooking and washing in the evening gets more from one than a house that stands empty until late.

If you have an electric car, some EV tariffs have a long cheap window overnight that a battery can use too. Tariffs and their cheap periods change, so look at what your supplier offers now before deciding.

Fitted in a home, a battery on its own falls under the same VAT relief for energy-saving materials as panels do, and that zero rate lasts until 31 March 2027.

Adding a battery to solar you already have

A battery can usually be added to an existing solar system. How it joins depends on the inverter already fitted, because some were made to take a battery. Where yours wasn't, the battery comes with an inverter of its own and connects on the mains side of the house.

Have the paperwork from the original installation to hand for the survey. The certificate and the inverter details show straight away what can be connected to what.

Panels that went up some years ago may sit on a board that has changed since, or one that never had the two-way protective devices a battery calls for now.

Where a home battery can go

PAS 63100, the fire-safety specification for batteries in homes published by BSI, lists the places a battery should not be installed. Bedrooms are on the list, along with any cupboard that opens into one.

The hall, the landing and anything else on the way out of the house are ruled out too, as are lofts and roof voids. A cellar with no way out to open air is excluded, and a battery shouldn't sit close to stored fuel or anything else that burns easily.

That usually leaves the garage or an outside wall. A battery indoors needs fresh-air ventilation to the outside, and the room it stands in should be separated from the escape routes by fire-resisting walls and ceilings.

Outside, it should sit away from doors, windows, vents and the route out of the house. Beside a driveway or in a garage it needs an enclosure tough enough to survive a knock from a car, or a barrier in front of it.

There's a cap on the total energy stored in one house too, set higher for batteries outdoors or in a detached garage than for batteries indoors.

The specification covers homes up to a set floor area. For a larger house it suggests taking advice from a fire safety specialist.

Smoke alarms where a battery is fitted

If the battery is somewhere you rarely go, such as a store cupboard, PAS 63100 asks for a smoke alarm or multi-sensor alarm in that space, interlinked with the rest of the alarms in the house so a fire there sets them all off. The same applies to an inverter in a loft or a cupboard.

It goes further for the whole house, recommending interlinked alarms on the escape routes and in rooms with a higher fire risk wherever a battery is installed. In an older house with one smoke alarm running on its own battery in the hall, that can mean new mains-powered interlinked alarms, which I fit myself.

Batteries and power cuts

A battery only keeps the lights on in a power cut if the system is built for it. One connected alongside the grid is set up to disconnect itself when the grid supply goes off, so it can't push power out into cables that may be under repair.

A backup system adds a changeover switch that separates the house from the grid first, then runs the whole house or a few chosen circuits, such as the fridge and the lights. The rules on alternative supplies say a source switched in like that must not be able to operate alongside the grid at the same time.

If backup matters to you, raise it at the survey, because it changes both the equipment and the wiring at the consumer unit.

A battery and the consumer unit

A battery charging from the grid adds a heavy load at the cheap-rate time, often while an electric car charger is running too.

The board needs space and suitable protective devices for both, and with an older board the first step may be replacing the consumer unit.