A south-facing roof in Cranleigh makes about three and a half times as much electricity in June as in December. PVGIS, the European Commission’s solar model, puts a 4 kWp array here at about 501 kWh in June and about 140 kWh in December. For anyone hoping the roof will run the car, that one gap matters more than any other figure.
What follows works through the months, with the daily sums labelled as ours. It assumes the car charges on a home charger of the kind covered on our Cranleigh EV charger page, with a compatible setup that can send surplus solar to the car.
The year in four months
All four figures below come from one PVGIS run for a 4 kWp array at 35°, facing due south, with 14% system losses, at Cranleigh’s village-centre point. The daily averages divide each month by its number of days.
| Month | PVGIS output | Daily average (our arithmetic) |
|---|---|---|
| June | about 501 kWh | about 16.7 kWh |
| July | about 500 kWh | about 16.1 kWh |
| December | about 140 kWh | about 4.5 kWh |
| January | about 157 kWh | about 5.1 kWh |
Across the whole year the same array makes about 4,086 kWh, an average of about 11.2 kWh a day. That annual average hides the swing: it is roughly two-thirds of a June day and two and a half December days.
The house takes its share first
Solar electricity goes to whatever is running in the house at that moment before anything else can use it. Ofgem’s Typical Domestic Consumption Value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day on average. Not all of that falls in daylight, but it is the right yardstick for what the house claims before the car gets anything.
That gives a fair way to read the table. Take a June day: about 16.7 kWh generated. Suppose, generously, that the house used its whole day’s 6.8 kWh while the sun was up. About 9.8 kWh would still be left for the car, on our arithmetic. Any of the house’s use that falls after dark leaves more for the car, but PVGIS gives long-run monthly averages, and individual days sit well above and below them.
June and July: what a summer surplus can add
Around 9.8 kWh is about an hour and twenty minutes of a 7 kW charger’s draw, or roughly a sixth of a 60 kWh charge, on our arithmetic. Repeated across the sunny days of June and July, that adds up to a real contribution, provided the car is plugged in during the day.
That last condition is the one people underestimate. Solar can only charge a car that is on the drive while the sun is up. Across Waverley, 50.7% of households had two or more cars or vans at the 2021 Census (ONS TS045), and in a two-car GU6 household it is worth asking which car is at home in daylight and pointing the surplus at that one. Where every car leaves early and returns late on weekdays, the surplus mostly goes to the grid, and weekends do the solar charging.
December and January: the off-peak window does the work
In December the sums run the other way. About 4.5 kWh a day generated is less than the 6.8 kWh an average household uses, so on a typical December day there is no surplus at all. January, at about 5.1 kWh a day, is little better.
So winter charging is a tariff question. Every home chargepoint sold in Great Britain since 30 June 2022 has had to be smart, able to schedule charging into cheaper hours. The EnSmart SmartBee-M we fit does that, so the car fills in an off-peak window overnight. Planning on that basis, rather than counting on the roof, avoids disappointment.
Spring and autumn
PVGIS reports every month, but we have quoted only these four here, so we are not putting figures on March or October. The shape is clear from the table: output climbs from a January low to a June–July peak and falls back. The months either side of the peak are where a household is most likely to notice solar charging start and stop.
What makes diversion work in practice
Three things decide how much of the roof’s output reaches the car. The car must be plugged in during daylight. The charger and the solar system must be set up to work together, which is a compatibility question to settle at the survey rather than assume. And the household needs to accept that summer charging is variable, because the table shows averages, not a daily promise.
If you are still weighing panels, our page on solar panels in Cranleigh covers the roof side. For the charger itself, see our home EV charger guide.
The paperwork, briefly
Cranleigh is in UK Power Networks’ South Eastern Power Networks area, about 5 km inside it. The installer notifies UK Power Networks of the chargepoint, and notifies panels separately under G98 or applies under G99 for a larger system. A home charger installation is standard-rated for VAT at 20%, while residential solar panels are zero-rated until 31 March 2027. If you rent, or own and live in a flat with private off-street or allocated parking, our guide to who qualifies for the EV chargepoint grant explains the 75% grant, up to £500 per socket; claims must be made through an OZEV-authorised installer; tell us your situation at the quote stage.
DVLA records 5,670 privately kept plug-in vehicles across Waverley at the end of June 2026, up from 4,375 a year earlier. More of them will be parked under a roof that could help in summer, and will need an off-peak tariff in winter.
Sources: European Commission JRC, PVGIS 5.3 (PVGIS-SARAH3, 2005–2023), 4 kWp, 35° tilt, due south, 14% losses, building-mounted, run 15 October 2026; Ofgem, Typical Domestic Consumption Values (from 1 July 2026); ONS Census 2021, TS045 Car or van availability, via Nomis (read 19 October 2026); Electric Vehicles (Smart Charge Points) Regulations 2021; UK Power Networks licence boundaries (December 2024) and NESO GB DNO licence areas (May 2024); Energy Networks Association, EREC G98 Issue 2 (10 March 2025); HMRC, VAT Notice 708/6; DfT and DVLA, VEH0142 licensed plug-in vehicles by local authority, private keepers (published 23 September 2026); GOV.UK, Changes to electric vehicle chargepoint grant schemes from 1 April 2026 (updated 7 July 2026).