Home EV Charging Cost Calculator UK 2026

Most EV owners do the majority of their charging at home overnight, but it can be surprisingly hard to know exactly what each session costs. This calculator works out the precise cost of a home charging session based on how much energy your car actually draws from the grid — accounting for the small losses that occur during charging — and converts that into a cost per mile so you can compare directly with petrol.

Your car & charge
Energy tariff
Charging efficiency — what's this?

Not all electricity drawn from the wall ends up stored in the battery. A small amount is lost as heat during the charging process. For home AC charging, 10% loss (90% efficiency) is a typical figure. You can leave this at the default unless you want to fine-tune the calculation.

Your results

Session cost
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Grid energy drawn
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Range added
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Cost per mile
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Petrol equivalent
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On Octopus Intelligent Go, this charge would cost — instead — a saving of —. Get Octopus Intelligent Go →

How this calculator works

The calculator first works out how much energy is added to the battery (battery size × charge percentage increase). It then grosses that up by the charging efficiency to find how many kWh you actually draw from the wall — this is what your electricity meter measures and what you're billed for. The session cost is simply the grid energy multiplied by your tariff rate.

Range added is calculated from the energy entering the battery (before efficiency losses), divided by your car's efficiency in miles per kWh. Cost per mile is the session cost divided by range added.

The petrol comparison

The petrol equivalent shown uses 40 MPG and the current UK average petrol price of 145p/litre as a reference point — you can compare this directly with the EV session cost for the same range. Adjust inputs to match your actual petrol car for a more personal comparison.

Why charging efficiency matters

Home AC charging (7kW wallbox or 3-pin plug) typically runs at 88–92% efficiency. DC rapid charging is generally more efficient (93–97%) but the rates are much higher. The default 90% is a good estimate for overnight home charging.