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Why doesn’t charging match the bill?

30 September 2026 · Written by Wattlas

The charger and the electricity meter aren't measuring the same thing. Here's how a 10 kWh charge could show up as 9 kWh on the meter.

A worked example, not customer data
Where the energy goes In this example, 9 kWh comes through the electricity meter: 7 to the car and 2 to the home. Another 3 kWh of solar supplies the car, so the charger records 10 kWh. Solar 3 kWh Grid · meter reads 9 kWh 7 kWh to the car 2 kWh to the house Car · charger reads 10 kWh House

Solar supplied part of the charge. The meter also counted the house.

What if I don't have solar?

The meter still includes the rest of the house. Check the dates too: an overnight charge can fall across two days.

And the cost?

Check the tariff saved in your charger app. If the rates are out of date, its cost estimate can be out of date too. Ohme explains how its tariff settings work.

A charge scheduled by your supplier may get the cheap rate outside the normal overnight hours. Check Octopus's current conditions before treating a daytime charge as off-peak.

See the charge and the rate together

Connect your supported charger and tariff to Wattlas to see them on the same day. Add compatible solar or battery data if you have it.

Wattlas can apply smart-charging rates and free sessions where the connection provides them. Other sessions can be added by hand. The import cost covers the whole home, not just the car.

See home charging in Wattlas, or check your charger and supplier. For billing questions, check with your supplier.

Sources checked 30 September 2026. Wattlas is independent of the suppliers and manufacturers mentioned.