The short answer
Solar panels need daylight, not heat, so they work all year. But UK winter days are short and the sun is low, so output drops a lot. A typical 4.5 kW system might make several times more on a good summer day than on a grey December day.
According to Utilita, around 69% of a typical home's yearly solar generation happens between April and September.
Cold, snow and frost
- Cold is fine. Panels actually work slightly more efficiently when they're cool.
- Snow blocks light until it slides off, which it usually does quickly from a sloped roof in sunshine. Don't climb on the roof to clear it.
- Frost usually melts off by mid-morning.
Getting more value in winter
- Run appliances in the middle of the day when there's most daylight, such as the washing machine or dishwasher.
- A battery with a time-of-use tariff can charge on cheap overnight electricity in winter, when the panels make little.
- Check your export rate. In summer, you'll export more, so a good rate matters. See export rates.
Yearly payback figures already include the darker months. See are solar panels worth it?
Sources: Utilita.