The Short Answer
Yes, solar panels can charge an electric car, and a typical 4kWp system makes more than enough electricity over a year for an average driver: about 3,800kWh against the 2,150kWh an average EV needs. But the timing is awkward. Most of it arrives on summer middle-days, when many cars are parked at work, and in December the same system makes a third of its June output.
The other thing almost nobody tells you: if you're on a cheap EV night tariff, charging the car from your solar can be worth less than exporting it. Night charging costs 7.6p a kWh on Intelligent Octopus Go, and Octopus's Outgoing export tariff pays 12p. Solar charging makes most sense if you don't have a night tariff, or you're home in the day and your export rate is low.
How Much an EV Needs, and What Solar Makes
An average driver doing 7,100 miles a year at 3.3 miles per kWh needs about 2,150kWh, or just under 6kWh a day. A typical home uses another 2,500kWh a year, Ofgem's current benchmark. Here's what a 4kWp south-facing system in the Midlands makes on an average day each month, from the European Commission's PVGIS solar model:
| Month | Average solar per day | Car's average need per day |
|---|---|---|
| December | 4.8kWh | 5.9kWh |
| February | 7.6kWh | 5.9kWh |
| April | 14.4kWh | 5.9kWh |
| June | 15.2kWh | 5.9kWh |
| August | 13.6kWh | 5.9kWh |
| October | 8.0kWh | 5.9kWh |
PVGIS v5.2, Birmingham, fixed at 40 degrees facing south, 14% system loss, scaled to 4kWp. Annual total about 3,900kWh, in line with the 3,800kWh we use for central England elsewhere on the site.
From spring to early autumn there's comfortably enough for the car and the house on most days. In the darkest months there isn't enough for either, so the car will need grid or night-tariff charging.
The Timing Problem, and How Chargers Solve It
Solar only charges a car that's plugged in while the sun is up. If you commute by car, that's mostly weekends. If you work from home, are retired, or have a second car that stays on the drive, it's most days.
Solar-matched chargers, such as myenergi's zappi, watch how much power your panels are sending to the grid and divert that surplus into the car instead. In zappi's ECO+ mode it waits for spare solar and starts once there's enough surplus, nominally 1.4kW on a single-phase charger, then follows your solar output up and down. Its ECO mode tops up from the grid to keep charging when the sun dips. A common approach is solar-only charging in summer and a night-tariff timer in winter.
That 1.4kW threshold matters. A small array on a cloudy day, after the house has taken its share, often won't reach it. Bigger arrays get there more often.
Is It Worth Using Solar for the Car? It Depends on Your Tariffs
Each kWh of solar can do one of three things: run the house, charge the car, or go to the grid. What it's worth in the car depends on what you'd otherwise pay to charge it and what you'd be paid to export it:
| Your setup | Charging the car otherwise costs | Exporting instead earns | Better use of a spare solar kWh |
|---|---|---|---|
| Standard tariff, Outgoing Octopus export | 26.32p | 12p | Charge the car (worth 14.32p more) |
| Intelligent Octopus Go, Outgoing Octopus export | 7.6p | 12p | Export it, and charge the car overnight |
| Octopus Go or British Gas EV Power, a 5p legacy export deal | 9.5p | about 5p | Charge the car (worth about 4.5p more) |
So for the many solar owners who'd still be on a standard tariff, sending surplus solar into the car is the best thing to do with it. For someone on a cheap night tariff with a good export rate, it's often better to export in the day and charge at night. Check with your supplier whether your export tariff can sit alongside the EV import tariff you want.
Run Your Own Numbers
Your system size, where you live, how often the car is home in daylight and your tariffs all change the answer. This calculator puts them together, month by month:
Solar EV Charging Calculator
How much of your driving your roof could cover, month by month, and whether putting that solar in the car beats exporting it and charging at night. Solar output from the EU's PVGIS model.
A typical 3-bed semi has about 4kWp
2 for a weekday commuter, 5 to 7 if you work from home
Solar into the car
611kWh
28% of the car's 2,152kWh a year
Miles from your roof
2,015
a year, at 3.3 miles per kWh
Gain vs exporting it
£87
14.32p per kWh better than export
Solar output: PVGIS v5.2 for a south-facing system at 40 degrees with 14% losses, scaled to 4kWp (3,885kWh a year here). We assume the house uses 45% of its solar itself, our standard model for homes without a battery, leaving the rest as surplus. The car can soak up surplus only on the days it's home, up to a week's worth of driving at a time. Real solar-matching chargers need a minimum surplus to start (nominally 1.4kW on a single-phase myenergi zappi), so cloudy-day output often won't reach the car. Export rates: Outgoing Octopus 12p; typical older supplier deals around 5p.
What It's Worth in Pounds
Say a solar diverter puts 1,000kWh of your summer surplus into the car over a year, roughly half the car's needs, with the rest coming from the grid. On a standard tariff that's 1,000kWh you don't buy at 26.32p, so about £263 saved, minus the £120 you'd have earned exporting it at 12p: a net gain of about £143 a year. On Intelligent Octopus Go you'd have charged that 1,000kWh for £76 at night and given up £120 of export, so you'd be £44 worse off. Same panels, same car, opposite answers.
Do You Need a Battery Too?
Usually not for the car. A home battery and an EV are both batteries, and the car's is many times bigger. A home battery earns its keep shifting cheap night electricity, or your own solar, into the evening for the house. If you have an EV on a night tariff, the battery can fill up overnight at the same cheap rate, which is the strongest case for one. Our solar battery guide runs those numbers.
Sizing Solar With an EV in Mind
- Go a bit bigger than you would for the house alone. An average EV adds nearly as much again to a typical home's electricity use, and adding panels later means paying for scaffolding twice.
- East and west roofs help. They spread generation across the morning and evening, which suits a car that's home outside office hours.
- Plan the charger at the same time. If you want a solar-matching charger, fitting it on the same visit as the panels is usually simpler and cheaper than two separate jobs.
Our solar sizing guide covers how many panels fit your usage, and the solar panel costs guide what they cost. Solar panels have 0% VAT until 31 March 2027, after which it goes to 5%.
Charge your car from your own roof
A typical 4kWp solar system in central England makes around 3,800kWh a year. Get free quotes from MCS-certified installers for solar, with or without a battery. Takes about 60 seconds.
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