The formula
Cost = (Watts ÷ 1,000) × Hours × Price per kWh
Worked example
A 2,000 W heater running for 3 hours a day at 25p per kWh: 2 × 3 × 0.25 = £1.50 a day, about £45 a month.
Where to find your price
Your bill shows a unit rate per kWh plus a fixed daily standing charge. This calculator uses the unit rate only, because the standing charge is paid whatever you use. On a campsite, the pitch fee may include electricity or it may be metered; ask the site.
Frequently asked questions
How much does it cost to run a 1kW heater for an hour?
Exactly one unit (1 kWh), so the same as your price per kWh: for example 25p or 17¢.
What uses the most electricity?
Anything that heats: kettles, heaters, ovens, tumble dryers and immersion heaters. Electronics and LED lights use very little.