kWh, kW and m³ explained

Your energy bill shows electricity in kWh and gas in m³. Once you understand these units, you can work out what an appliance or a shower costs yourself.

Power: watts and kilowatts

Power tells you how much energy an appliance uses at any moment. It is measured in watts (W). 1 kilowatt (kW) is 1,000 watts. A 10 W lamp uses less at any moment than a 2,000 W (2 kW) kettle.

Energy: kilowatt-hours

How much energy you use in total depends on power and time. For that you use the kilowatt-hour (kWh): 1 kW for 1 hour.

• kWh = power in kW × number of hours
• kWh = power in W ÷ 1,000 × number of hours

Examples: 2,000 W for half an hour is 2 × 0.5 = 1 kWh. 10 W for 100 hours is also 1 kWh. You pay per kWh, so both cost the same.

Note the difference between kW and kWh: kW is a rate (like kilometres per hour), kWh is an amount (like kilometres).

Gas: cubic metres

Gas is measured in cubic metres (m³): the volume that passes through your gas meter. You pay the supply rate and energy tax per m³. Households mainly use gas for heating, hot water and cooking, so gas use is much higher in winter than in summer.

Net and gross electricity use

With solar panels you have two flows: electricity taken from the grid and electricity fed back. Net use is taken minus fed back. Until the end of 2026, net metering means you only pay for net use; see net metering.

From units to euros

Cost = number of units × price per unit. Use the price including energy tax and VAT. How to work it out is on price per kWh and m³.

Content reviewed on 26 September 2026.