See what petrol is really costing you.

Method. Your weekly petrol spend ÷ petrol price = litres a week. Litres × (100 ÷ your car's litres per 100 km) = km a week. Km × the electric car's kWh per 100 km ÷ 100 = kWh a week. kWh × the electricity price = electricity cost a week. A month is 52 ÷ 12 weeks; a year is 52 weeks. Electricity results are rounded to the nearest ₦100.

Electric car energy use. We use the European WLTP test where it exists. Where only a China test figure is published, we multiply it by 1.30, because China's test gives lower figures (for the BYD Sealion 7, China 15.2 vs WLTP 19.9 kWh/100 km). Plug-in and range-extended cars are counted as driving on battery power only.

Not in the list yet: BYD Leopard 8: No published kWh/100 km and no clear sibling version (only a battery ÷ range estimate).

Petrol cars. Official town-driving test figure for each model. Heavy traffic can use more. These figures come from different official tests, so treat them as a guide. Size options are our own rounded estimates, based on the official test figures in the list. For a pickup such as the Toyota Hilux, choose “My car isn't listed” and enter your own fuel use.

Estimate: cost per kWh = petrol price ÷ 1.0 kWh per litre (Honda EU2200i inverter generator at quarter load, fuel only; derived from Honda's published run times). Charging losses and less efficient generators are not included.

Your state. Each state starts with the electricity companies that serve it and the petrol price shown; you can change both. We start with the companies that serve each state. If yours is different, choose it from the list.