Does Solar EV Charging Work in Winter? A Month-by-Month Look
Published 20 October 2026 · Commercial Solar EV Editorial
Yes, but at a fraction of the summer rate. For a London workplace where cars are parked 09:00–17:00 on weekdays, an array half the size of the vehicles’ yearly demand supplies about 47% of their charging energy in June and about 10% in December. Double the array and the figures become 81% in July and 19% in December. The yearly share hides a strong seasonal swing, and a fleet that plans around the yearly number will see grid electricity carry most of its winter charging.
The month-by-month numbers
This is the share of a workplace fleet’s charging energy supplied by the array in each month, from an hour-by-hour simulation using PVGIS data for 2005–2023, a London array at a 10° pitch and chargers that follow the sun. The array sizes are expressed against the fleet’s yearly demand.
| Array (× demand) | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.5× | 12% | 19% | 30% | 43% | 44% | 47% | 46% | 40% | 35% | 23% | 14% | 10% |
| 1.0× | 23% | 37% | 59% | 77% | 77% | 81% | 81% | 75% | 67% | 45% | 29% | 19% |
The pattern has three parts. From April to August even the smaller array covers roughly 40% or more of the charging energy. In October the figure falls to under a quarter, and from November to January it is 14% or less for the smaller array. And the larger array does not fix the winter: it lifts every month, but December still sits at 19% because the limit is the winter sunlight, not the number of panels.
Why winter is so much weaker
Three things happen at once. Days are short, so fewer of the parked hours fall in daylight. The sun is low, so each panel produces less in the hours that remain. And weather is worse. A parked-in-daytime pattern still captures more of what is produced than an overnight one, but there is simply less to capture. The same effect is why the figures differ by city: the yearly output across the eight UK cities in the model runs from 759 to 951 kWh per kW.
The year-to-year spread
Even the yearly figure moves. London’s output ranged from 861 to 978 kWh per kW between 2005 and 2023, a spread of about 14% between the weakest year (2021) and the strongest (2022). A business case that only works in a sunny year is fragile; one that works in the weak year is safe.
What this means for a business
- Size on the year, not the month. Panels are bought for annual output and the economics are annual. A grid supply covers the winter gap; the chargers must be specified to do that without a fuss.
- Do not promise a flat solar share. A monitoring report that shows the solar share by month, rather than a single yearly figure, avoids surprises in January. The solar powered EV charger guide lists the report to ask for at handover.
- Control matters most when sun is scarce. In winter, charging that starts on arrival uses nearly none of the little there is. Solar-following control, covered in the load-management guide, is what captures it.
- A building that uses the output beats a car park that cannot. Where the site has weekday daytime demand, the array earns its keep on the building in winter too. The break-even test shows how the economics shift.
For the engineering behind these figures, including the minimum charging current that limits how small a surplus a charger can follow, see how solar EV charging works. To try your own parking hours, use the EV charging cost calculator.
Sources: EU JRC PVGIS 5.3 hourly series (SARAH3 radiation, ERA5 meteorology), 2005–2023, 14% system losses; the model assumptions are on the calculator page. Checked 20 October 2026.