Will Solar CCTV Get Through a UK Winter? Sizing Panels and Batteries for December

A solar camera installed in spring will run faultlessly all summer and tell you nothing useful about whether it was specified correctly. The test is the third week of December: barely eight hours between sunrise and sunset, thick cloud for days on end, a low sun that never gets above the hedge, and a camera that is being asked to run its infrared illuminator for sixteen hours a night. If a camera dropped out last winter, it almost certainly was not faulty. It was undersized, or badly sited, and September is the month to fix it — while there is still enough daylight to recharge a battery you have let run flat. Last updated: September 2026. The numbers that make winter hard In the south of England, a fixed panel generates roughly five times less usable energy in December than in June. Further north it is worse. Three things stack up at once: Short days. Eight hours of daylight, and only the middle few are worth much. Low sun angle. The sun barely clears the horizon, so a panel set at a summer angle catches very little of it. Cloud. A run of flat grey days can cut output to a fraction of clear-sky figures — and December routinely delivers a week of them back to back. Meanwhile, demand goes up. The camera runs infrared or white-light illumination for sixteen hours instead of eight, and battery chemistry itself delivers less usable capacity in the cold — a lithium pack at 0°C gives you noticeably less than the same pack at 20°C, and most will not accept a charge at all below freezing. So you are asking more of a system that is producing far less. That gap is what has to be designed for. Size for the worst week, not the average The mistake is to size against an annual average, or against what the camera drew during the install. Work the other way round: Start from the camera's real daily consumption in winter — including the illuminator, including the 4G radio transmitting clips overnight, not the idle figure on the datasheet. Assume the panel gives you very little for several days running. A realistic design target for a UK winter is a battery that will carry the camera for three to five days with no meaningful charge at all, so a grey week does not empty it. Oversize the panel rather than the battery where you can. A bigger panel harvests more from the few bright hours you get; a bigger battery only stores what the panel manages to put in. Both matter, but a system that never fully recharges will fail no matter how large the battery is. As a rule of thumb for a single 4G camera on a UK farm, a panel and battery that look generous in summer are about right for December. If the kit looks exactly adequate in June, it will not make it through. Siting matters more than specification in winter A well-sited modest panel beats a large badly-sited one every time, and the difference is starkest in December. Face it due south, and steepen the angle. A panel set near-vertical (around 60–70°) catches a low winter sun far better than one lying back at a summer angle — and sheds snow and leaves instead of collecting them. Watch the winter shadow line, not the summer one. The sun tracks much lower, so a hedge, barn or belt of trees that casts no shadow in July will put a panel in shade all morning in December. Stand at the panel position in September and look south at midday — anything on that horizon will be a problem in three months. Get it up out of the way of splashing mud, drifted snow and curious stock. Keep it clean. A winter's worth of grime, moss or bird mess on the glass costs real output at exactly the point you cannot spare any. One wipe in November and one in January is the cheapest maintenance there is. Reduce the demand side Half the winter problem is solved by asking the camera for less between November and February: Cut the illumination. Continuous white light is the single biggest overnight drain. Switch to infrared, or to a mode that only lights up when something is actually detected. Record on event, not continuously. Motion- or AI-triggered recording, with a sensible detection zone, dramatically reduces both power and data. Our guide to AI detection and cutting false alarms covers tuning the triggers so the camera is not waking for every swaying branch. Drop the upload quality overnight, or hold clips on the SD card and upload on a schedule. Turn off what you are not using — the spotlight, the siren, the second stream. Fix a weak signal. A camera on a marginal 4G signal transmits at full power and retries constantly, which costs far more battery than most people expect. Improving the antenna often improves the power budget as much as the picture. When solar genuinely is not the answer Some positions cannot be made to work on sun alone — a north-facing yard, a wooded valley, a camera under a canopy, or a site that needs continuous recording rather than event clips. The honest options there are: Mains, if it is anywhere near. Even a long armoured run is often cheaper over three years than repeated winter callouts. A hybrid: solar with a mains or generator top-up for the eight worst weeks. A bigger battery bank with a planned swap — two batteries, one on charge in the workshop. Move the radio, not the camera. Where the constraint is a weak signal rather than sun, linking the camera back over Wi-Fi HaLow to one well-fed uplink removes the 4G drain from every camera on the holding. A September checklist Walk every camera and note which ones struggled last winter, and when. Clean the panels and check the glass, cable glands and connectors for water ingress. Re-angle panels steeper for winter and check the southern horizon for new growth. Check battery health — a pack that has been cycled hard for two or three seasons will not hold what it once did, and winter will expose it. Switch illumination and recording settings to their winter modes now rather than in December. Replace anything that was marginal. It will not improve on its own. Not sure whether your setup will make it through? Tell us…