In June, a south-facing 4 kWp roof in Chelmsford averages about 16.6 kWh a day on the European Commission’s PVGIS figures. In December, the same roof averages about 4.7. Those two numbers decide how much of a car’s charging a roof can carry across the year, and this guide works through both months with the arithmetic shown. For fitting the charger itself in CM1, CM2 and CM3, see our Chelmsford EV charger page.
The question is a live one for the city’s drivers: about 5,507 plug-in vehicles were privately kept across the Chelmsford city council area at the end of June 2026, up from 3,996 a year earlier (DVLA), 1,511 more in a year. This is a charging guide, not a solar quote. What panels would make on your own roof, and the survey that answers it, is covered on solar panels in Chelmsford.
The two months on one Chelmsford roof
| June | December | |
|---|---|---|
| Month’s output, PVGIS | about 499 kWh | about 145 kWh |
| Daily average (our arithmetic) | about 16.6 kWh | about 4.7 kWh |
| Hours at the full 7 kW if every kWh went to the car (our arithmetic) | about 2 hours 20 minutes | about 40 minutes |
The run uses PVGIS 5.3 for Chelmsford with 4 kWp of panels at a 35° tilt, facing due south, with 14% system losses and no shading, run on 15 October 2026. East- and west-facing roofs make less, and trees or a neighbouring building change the answer more than the town does. We print only June and December here; the survey runs the figures for your own roof.
The house takes its share first
Panels feed the house before anything else. Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day if spread evenly (our arithmetic). Real use is not even: some falls at night, when the panels make nothing, which leaves more of the daytime output spare; some falls on a busy afternoon, which leaves less. Treat 6.8 kWh as a yardstick for a Chelmsford semi or terrace, not a measurement of your house, and use your own meter readings if you have them.
A June day, worked through
Take the June average: about 16.6 kWh from the roof, less about 6.8 kWh for the house, leaves roughly 9.8 kWh (our arithmetic). Against a 60 kWh car battery, that is about a sixth of a full charge. Over the whole of June, the roof’s 499 kWh against roughly 204 kWh of household use leaves about 295 kWh, close to five full charges, if every spare kWh found the car (our arithmetic).
It rarely will, for three reasons. The car has to be at home and plugged in while the sun is up. The surplus rises and falls with cloud, and the charger has to follow it. And a car that is already full takes nothing. For a household whose car sits on a Springfield or Great Baddow drive through the day, a real share of summer charging can come from the roof; for one whose car leaves early and returns at six, much of June’s surplus will be exported instead.
A December day, worked through
In December the arithmetic turns round. About 4.7 kWh a day from the roof is less than the house’s 6.8 kWh average (our arithmetic), so on a typical December day there is nothing spare for the car at all. Across the month, the roof’s 145 kWh sits against roughly 211 kWh of household use. A Chelmsford car charged in December is charged from the grid, whatever is on the roof, and that answer does not depend on the make of charger or panel.
Between the two
PVGIS gives the bracket; the Met Office gives the shape. Its station at Writtle, under two miles west of the city centre, averaged 1,643.9 hours of sunshine a year over 1991–2020, with July the sunniest month at about 217 hours and December the dullest at about 52. On those figures the months when solar charging carries real weight sit in the middle of the year and taper towards each winter, so a Chelmsford driver planning around the roof should think in seasons rather than in days.
Making the charger follow the sun
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. That lets a charger follow a schedule and, with a compatible setup that reads what the house is exporting, follow a solar surplus instead. Whether a particular combination of charger, sensor and inverter can do that is something we confirm at the survey for the exact kit involved. If your home is one of the roughly 5,254 solar PV installations DESNZ records across the city council area (all sizes, end of 2025, as first published), bring the inverter’s make and model to that conversation. Our home EV charger installation guide sets out the SmartBee-M’s published specification.
Which Chelmsford homes can do this
Solar charging needs a roof that gets the sun and a parking space the cable can reach, on the same property. At the 2021 Census, 31.9% of households in Chelmsford’s built-up area lived in semis and 20.0% in detached houses, where a drive and a roof of your own are the usual case. For the 26.2% in flats, the roof and the car park usually belong to a freeholder. For the 21.8% in terraces without off-street space, Essex Highways says a charging cable across the public footway is illegal and not permitted, and cross-pavement channels are not currently permitted while it develops a trial framework (its EV strategy page, read 19 October 2026). Renters and flat owners with private off-street or allocated parking can get OZEV’s charger grant, 75% of the cost up to £500 per socket, which must be made through an OZEV-authorised installer; tell us your situation at the quote stage. Our guide to who qualifies for the EV chargepoint grant covers each case.
Winter: the overnight schedule does the work
From late autumn to early spring, plan on the grid. A smart charger comes with default charging hours outside the regulations’ weekday peaks of 8am to 11am and 4pm to 10pm, and you can set it to your tariff’s own off-peak window instead. At roughly 7 kWh an hour, a 60 kWh battery fills from empty in about eight and a half hours (our arithmetic). Central Chelmsford sits in UK Power Networks’ Eastern Power Networks licence area, about 26.9 km from any other licence boundary; a 7.4 kW charger draws 32 A continuously, the survey checks it against your main fuse, and the installer notifies UKPN of the chargepoint.
Sources: PVGIS 5.3 (European Commission JRC), PVGIS-SARAH3 2005–2023, 4 kWp, 35° tilt, due south, 14% system losses, Chelmsford, run 15 October 2026; Ofgem, Typical Domestic Consumption Values (from 1 July 2026); Met Office, Writtle location-specific long-term averages, 1991–2020; legislation.gov.uk, The Electric Vehicles (Smart Charge Points) Regulations 2021, regulations 1 and 10, read 19 October 2026; Department for Transport and DVLA, VEH0142 licensed plug-in vehicles by keepership and local authority, Chelmsford, private keepers, end of June 2025 and end of June 2026 (published 23 September 2026); DESNZ, Renewable electricity by local authority, 2014 to 2025 (published 29 September 2026); ONS, Towns and cities, characteristics of built-up areas, England and Wales: Census 2021, tables 1c and 5c, Chelmsford BUA; Essex Highways (Essex County Council), EV strategy, https://www.essexhighways.org/ev-strategy (read 19 October 2026); OZEV, Changes to electric vehicle chargepoint grant schemes from 1 April 2026 (updated 7 July 2026); UK Power Networks, Licence Boundaries open dataset (17 December 2024); NESO, GIS boundaries for GB DNO licence areas (3 May 2024).