A UK winter is the hardest test for a solar system. Days are short, the sun sits low and cloud is common. Your panels will make much less in December than in June, and it helps to know that before your first winter rather than during it. Here is what changes, and what a battery does about it.
What the panels make
Solar output follows daylight. In summer, panels generate from early morning into the evening; in midwinter, the useful window is a few hours around midday, with the sun much lower in the sky. Most of a year’s generation comes between spring and early autumn. When we model your system we look at the whole year, not a sunny-day snapshot, so the winter dip is already in your figures.
Cold itself is not a problem. Panels run on light, not heat, and work slightly more efficiently on a cold, bright day than on a hot one. Snow is different: a covered panel makes little until the snow slides or melts off. Please do not climb up to clear it yourself.
Where the battery earns its keep
In summer, a battery mostly stores your own solar for the evening. In winter, when there is less spare solar to store, it can charge from the grid overnight on a time-of-use tariff instead, at the cheap rate, and run the house through the expensive hours. That is why a battery keeps saving money in the months when the panels do least. Our guide to battery-only savings shows how that works on its own.
Power cuts
Winter storms bring power cuts. With a backup gateway fitted, your battery can keep the home running when the grid goes down. The app lets you set how much charge the battery keeps in reserve for this, and you can raise it when a storm is forecast.
The battery itself
Both batteries we fit, Powerwall 3 and SigenStor, are rated for installation indoors or outside. We agree the position with you at design stage, and a garage, utility room or sheltered wall all work well.
Making the most of winter
- Use a time-of-use tariff. It is what lets the battery save money when the sun does not.
- Run big appliances around midday. On a bright winter day, the washing machine or dishwasher at lunchtime makes the most of the solar there is.
- Judge it over a year, not a week. A quiet week in January is normal. If something does look wrong in the app, our support team can check your system remotely, with your permission.
Want to see how your home would do across a whole year? Try our savings calculator, or ask us for a proposal modelled on your actual roof and usage.
This guide is general information, not advice for your specific property. Every Powergy proposal is modelled on your actual roof, usage and tariff.