June and December are the two months to look at if you want to know how much of a car a Guildford roof can charge. On PVGIS, the European Commission’s solar calculator, a 4 kWp south-facing array at the town-centre point makes about 486 kWh in June and about 130 kWh in December. That gap shapes everything else in this guide.
The charger itself, its circuit and the paperwork are covered on our page about EV charger installation in Guildford. Here we look only at the sun: what it can add to a car parked in Onslow Village or Stoughton, month by month, using published figures and arithmetic we label as ours.
Two months that tell the story
Divide each month by its days and June comes out at roughly 16.2 kWh a day, December at roughly 4.2 kWh a day (our arithmetic). The year as a whole is about 3,974 kWh on PVGIS, or about 10.9 kWh a day, so an annual figure on a quote can make a Guildford roof sound steadier than it is. The Met Office station at Wisley, about six miles north-east of the town, explains why: about 208 hours of sunshine in July against about 47 in December, on its 1991–2020 averages.
These PVGIS figures assume an unshaded, due-south roof at 35°. A Guildford semi in Boxgrove with an east-west roof, or a Merrow house shaded to the south by a neighbour’s tree, will make less. Read them as an upper guide, not a forecast for your own roof.
What a June surplus can add
A car only takes solar if it is plugged in while the roof is generating, and the house takes its share first. Ofgem’s typical domestic consumption value, from 1 July 2026, is 2,500 kWh a year, about 6.8 kWh a day (our arithmetic). Not all of that is used in daylight, so taking the whole of it off a June day is a cautious assumption. Even so, an average June day in Guildford would leave about 9.4 kWh for the car.
At 7 kW, 9.4 kWh is about an hour and 20 minutes of charging; it is about a sixth of a 60 kWh charge (our arithmetic). Over the whole month, the same sum leaves up to about 280 kWh, which on paper is more than four 60 kWh charges. In practice it arrives in pieces: a little on a cloudy morning, more on a clear afternoon, nothing while the car is at the station car park or in the office. For a household where someone works from home in Shalford or Jacobs Well and the car sits on the drive, a good part of summer driving can come from the roof. For a commuter whose car leaves at seven, much less.
What December looks like
On the same assumptions, December reverses the picture. About 4.2 kWh a day is roughly 36 minutes at 7 kW if nothing else used it (our arithmetic), and something else always does: 130 kWh across the month is about 61% of a typical household’s average use over 31 days, before any car is plugged in (our arithmetic). In winter the roof is covering part of the house’s daytime use, not charging the car.
That is why winter charging on a Guildford drive is an off-peak job. Every new home chargepoint sold in Great Britain has had to be smart since 30 June 2022, under the Electric Vehicles (Smart Charge Points) Regulations 2021, so the charger can be set to fill the car in a cheaper overnight window. Your supplier sets the tariff and its hours; the charger follows the schedule.
The months in between
January is only a little better than December: PVGIS puts it at about 152 kWh for the same roof, roughly 4.9 kWh a day, while July, at about 491 kWh, is roughly 15.8 kWh a day (our arithmetic). Spring and autumn sit between those two ends. A sensible way to think about a Guildford year is two seasons: from late spring to late summer the roof can contribute to the car on most dry days, and from late autumn to late winter the smart schedule does the work. A Guildford household should not buy panels expecting the car to run on sunshine in February.
If you are weighing panels for the house first, our post are solar panels worth it in Guildford works through the payback; this one only asks what is left for a car.
Getting the surplus to the car
Three things decide whether a Guildford summer surplus actually reaches the car. The panels and the charger have to work together, so that the charger takes only what the roof is exporting. The car has to be at home and plugged in during daylight. And the house’s own use comes first. Which combinations work is a question for the survey, with your panel and inverter details in hand, because it depends on what is already fitted. The EnSmart SmartBee-M we fit is a smart charger with WiFi and Ethernet connectivity on its published specification; our home EV charger installation page covers it.
If you have no panels yet, our page on solar panels in Guildford covers the roof side. Any new array needs the network operator told or asked, and that is the installer’s job. Guildford town centre is on UK Power Networks’ South Eastern Power Networks area; towards Worplesdon and Normandy, check your address with the Energy Networks Association’s postcode tool rather than assuming.
What to bring to a survey
- Your panel and inverter details, if you have panels, and roughly when the car is at home.
- A year of electricity use, which tells us how much of the roof’s output the house already takes.
- The tariff you are on or are considering, so the winter schedule fits its off-peak hours.
Owner-occupiers of Guildford houses have had no chargepoint grant since April 2022; flat owners and renters can see who qualifies in our EV chargepoint grant guide.
Sources: PVGIS 5.3, European Commission Joint Research Centre (PVGIS-SARAH3 2005–2023; 4 kWp, 35°, due south, 14% losses; run 15 October 2026); Met Office, Wisley station 1991–2020 averages; Ofgem, typical domestic consumption values from 1 July 2026; Electric Vehicles (Smart Charge Points) Regulations 2021 (S.I. 2021/1467); EnSmart Power, SmartBee-M specification as listed by its UK distributor; Energy Saving Trust, Battery storage (updated 19 August 2026); UK Power Networks licence boundaries (December 2024) and NESO GB DNO licence areas (May 2024); GOV.UK, Changes to electric vehicle chargepoint grant schemes from 1 April 2026 (updated 7 July 2026). Daily figures, surpluses, charging times and shares are our arithmetic on these rows.