Solar panels and batteries

Solar panels

Panels make most electricity in summer and in the middle of the day. South-facing roofs produce the most; east and west-facing roofs still work well and spread output across the morning and evening. Shade from trees, chimneys or neighbouring buildings cuts output more than the direction does.

You use what you can while it is being made, and the rest goes to the grid. In England, Scotland and Wales, larger energy suppliers must offer to pay for what you export under the Smart Export Guarantee. Rates vary a lot between suppliers and you don't have to use your own supplier: see tariffs. You need an MCS-certified installation and a smart meter.

In England most roof-mounted panels are permitted development. Listed buildings, conservation areas and flat roofs have extra conditions. See the Planning Portal.

Solar with a heat pump

A heat pump uses most electricity in winter, when panels make least. Over a year the two still work well together, mostly by covering hot water and the rest of the house in the lighter months. Don't expect panels to run the heating in January.

Batteries

A battery moves electricity from when it is made or cheap to when you need it: midday solar to the evening, or cheap overnight grid electricity to the next day. It pays back best on a tariff with cheaper hours, and helps less if you are at home using electricity during the day anyway.

Home batteries are sized for an evening or a day, not for storing summer sunshine for winter. Most don't keep the lights on in a power cut unless they are fitted with a backup circuit, so ask if that matters to you.

What size for your home

The savings calculator suggests a size of array and battery for your address and estimates what they'd save. Installers should check the roof and your usage before quoting.