How accurate are the solar generation figures used in this calculator?

The regional figures are reasonable UK averages, but actual generation depends on roof orientation, shading, and local weather.

Solar EV Charging Savings Calculator

Q: Is charging my car from solar really free?

Not entirely, if you are paid for exporting unused solar power. Using it to charge your car instead of exporting it means giving up that payment, so the real saving is the gap between what you pay to buy electricity and what you would have earned selling it back.

Q: Should I charge my car during the day instead of overnight?

If you are often home during the day and do not have a battery, yes, since this lets you use solar power directly as it is generated. Some smart chargers can also do this automatically.

See how much of your EV charging your solar panels could cover, what that's really worth in money, and how much CO₂ it saves — just answer a few simple questions, no technical knowledge needed.

How big is your solar panel system?

System size (kWp)

Roughly where do you live? Solar panels generate a bit more in sunnier southern areas

Do you have a home battery?

Roughly how big?

Battery size (kWh) Check your battery's spec sheet or app if unsure

When do you mostly charge your car?

What car do you drive?

Roughly how many miles do you drive a year? The average UK driver covers around 7,000-8,000 miles a year

What do you pay for electricity? (pence per unit) Check a recent bill — this is your price per kWh

Do you get paid for unused solar power? If you're on an export scheme (like SEG), enter the rate in pence per unit — otherwise enter 0

Your car needs

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Your solar covers

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You could save

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CO₂ saved / year

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Why the saving isn't just "free electricity"

It's tempting to think solar-charged miles are completely free, but if you get paid for exporting unused solar, that's not quite right. Every unit of solar power you use to charge your car is a unit you're not sending back to the grid for payment. So the real saving is the gap between what you'd have paid to buy that electricity, and what you'd have earned selling it — not the full price. This calculator works it out properly rather than overstating how much you'll save.

How much of your charging can solar realistically cover?

Your situation	How much solar typically helps
Charging overnight, no battery	Not much — your panels aren't generating while you charge
Charging during the day, no battery	A decent amount — you're using the power as it's generated
Charging overnight, with a battery	Better — the battery saves up daytime solar for later
Charging during the day, with a battery	Best — direct solar, plus stored power to top up any shortfall

These are general patterns rather than guarantees — your actual results depend on the weather, your roof, and how your system is set up. Some smart chargers can automatically use spare solar power first, which can improve on these general figures.

Further reading:
Solar PV combiner boxes explained
EV charging cost & time calculator
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Frequently Asked Questions

Is charging my car from solar really free?

Not entirely, if you're paid for exporting unused solar power. Using it to charge your car instead of exporting it means giving up that payment, so the real saving is the gap between what you pay to buy electricity and what you'd have earned selling it back.

Do I need a battery to charge my car from solar?

No, but it helps a lot if you tend to charge overnight. Without a battery, solar can only help while the sun is actually shining. A battery stores daytime solar so it's still available later in the evening or overnight.

Should I charge my car during the day instead of overnight?

If you're often home during the day and don't have a battery, yes — this lets you use solar power directly as it's generated. Some smart chargers can also do this automatically, only charging when there's spare solar available.

How accurate are the solar generation figures used here?

The regional figures are reasonable UK averages, but your actual generation depends on which way your roof faces, how much shade it gets, and the local weather. A well-positioned, unshaded south-facing roof will do better than these figures suggest; a shaded or poorly angled roof may do worse.

This calculator provides estimates for general guidance only, based on typical figures and the information entered. Actual solar generation and savings depend on your specific system, location, and usage.

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