The short answer: charging from your own solar panels is cheap, but it is not free. Every unit that goes into the car is a unit you could have been paid to export. For some households, a cheap overnight tariff is cheaper still.
What a year of driving costs
For 7,400 miles a year in a car that does 3.5 miles per kWh, which is about 2,100 kWh:
| How the car is fuelled | Cost per year | Cost per mile |
|---|---|---|
| Petrol car, 40 mpg at 145p a litre | About £1,575 | 21p |
| Electric car on public rapid chargers | About £1,375 | 19p |
| Electric car at home on a standard tariff (26.32p) | £556 | 7.5p |
| Electric car on spare solar power (15p export given up) | £317 | 4.3p |
| Electric car at home on an off-peak tariff (7.5p) | £159 | 2.1p |
The petrol, public charging and off-peak rows are illustrative figures from a published running-cost calculator. The standard tariff and solar rows are our own calculations.
The part most guides miss
If you are on a good export tariff of around 15p per kWh and a cheap overnight car-charging tariff, you are better off selling your solar power in the day and charging the car at night. You earn 15p for each unit exported and pay about 7.5p to replace it.
Solar charging wins when:
- you have no off-peak tariff
- your export rate is low
- you currently rely on public chargers
- the car is at home during the day
Sizing the system
A typical 4 kW system generates about 3,400 kWh a year, and an average car needs about 2,100 kWh. If you want to cover both the house and the car, look at 5 to 6 kW. See cost by system size.
What you need
- A solar-aware charger. These divert spare solar power into the car automatically.
- A smart meter, for off-peak and export tariffs.
- Possibly a battery, if the car is away all day. See solar and battery costs.
An electric car charger can be included in a Warm Homes loan when it is installed with solar panels. See the Warm Homes loan.
Solar cost calculator UK edition
What would solar cost, and what would it be worth to you?
Six questions. No email address, no phone number. You get a size, a price range, a yearly figure and a payback range, with every assumption shown underneath.
Question 1 of 6
Your estimate
This is an estimate for general information, not a quote. It was correct at the time of publication and uses the assumptions shown. The performance of solar PV systems is impossible to predict with certainty, because sunlight varies from place to place and year to year. Only a survey by a certified installer can give you an accurate design and price. This is not financial advice.
Your answers go with you in this browser tab only, so the quote form does not ask again.
How we worked this out
| Assumption | Value | Source |
|---|---|---|
| Installed cost | 3 kW solar: £5,000–£6,000; 4 kW solar: £6,000–£8,000; 5 kW solar: £7,000–£9,000; 6 kW solar: £8,000–£11,000; 5 kWh battery: £2,500–£5,000; 10 kWh battery: £4,500–£8,000 | Published UK price guides, government installation cost data (2025/26) and MCS installation costs (2025) |
| Electricity price | 26.32p per kWh | Ofgem price cap, Direct Debit, October to December 2026 |
| Export rate | 15p per kWh | Which? fixed export tariff comparison, April 2026 |
| Output per kW | 850 kWh per year for a south-facing roof | National estimate used by this calculator: a 4 kW system generating 3,400 kWh per year |
| Roof direction factors | South: 100%; South-east: 95%; South-west: 95%; East: 82%; West: 82%; North-east: 67%; North-west: 67%; North: 55%; Flat roof: 90%; Not sure: 82% | Published UK output tables; indicative factors used by this calculator |
| Shade factors | No shade: 100%; Some shade: 90%; Heavy shade: 75% | Calculator estimates; an MCS installer measures shade on site |
| How home use is estimated | Home use of solar power is estimated using an approximation based on MCS 032 | |
Sources
Correct at the time of publication, 14 November 2026.
- Ofgem, energy price cap unit rates: https://www.ofgem.gov.uk/your-energy-supply/your-energy-bill/energy-price-cap-unit-rates-and-standing-charges
- GOV.UK, Warm Homes Loan Scheme: https://www.gov.uk/warm-homes-loan-scheme
- GOV.UK, Smart Export Guarantee: https://www.gov.uk/government/publications/smart-export-guarantee-seg-earn-money-for-exporting-the-renewable-electricity-you-have-generated
- Running-cost comparison figures, ExpertSure: https://www.expertsure.com/tools/ev-chargers/ev-charging-cost-calculator/