What Is a kWh?

Your electricity bill is priced in kilowatt-hours, kWh for short, and once that unit clicks, every other number on this site is a lot easier to read.

Think of kW as a tap: it’s how fast electricity is flowing right now. A 3kW kettle pulls power three times as fast as a 1kW lamp. kWh is the bucket you’re left holding once that tap has run for an hour. Leave a 1kW heater on for a full hour and you’ve used 1 kWh, about 26p at today’s typical unit rate. Boil a 3kW kettle for five minutes instead and you’ll use a quarter of that, roughly 6.5p.

Here’s what that looks like for a few everyday appliances:

Kettle, one boil 0.24 kWh ~6p
Washing machine, eco cycle 0.68 kWh ~18p
Tumble dryer, one cycle 2.5 kWh ~65p
EV home charge, 3 hrs at 7kW 21 kWh ~£5.46
Electric oven, 1 hour 2.2 kWh ~57p
Electric shower, 9 mins 1.28 kWh ~33p
Fridge-freezer, a full day 0.72 kWh ~19p
TV, an evening (4 hrs) 0.4 kWh ~10p

Figures assume a unit rate around 26p/kWh, the same assumption used across our calculators. Wattages are typical UK figures, not every model's nameplate rating, so your own appliances may draw a bit more or less.

Solar panels are rated the same way, in kWp (kilowatt peak): the fastest rate they can produce power in full sun. More sun-hours means more kWh generated, and more kWh generated means more pounds off your bill.

See what this means for your bill

Want to check an appliance that’s not listed above, or run your own numbers? Try the appliance running cost calculator. Curious about other terms you’ll see on a solar quote, like kWp, SEG or MCS? The glossary covers those too.

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