What is a kWh? kW and kWh explained

04 January 2017 | OVO Energy

This guide is intended to provide general guidance only. It is not intended to give you advice on your personal financial circumstances. You should seek independent professional advice if you’re unsure about anything mentioned in this guide or what choices to make.

When you get your electricity and gas bills, what do you look at? Of course most of us just look at the total cost to make sure we haven’t built up a large credit or debit balance. You may check the meter readings to make sure they match the ones on your meter.

But do you ever look closely at the number of kilowatt hours (kWh) you’ve used - and do you know what it means?

If you know what a kilowatt hour is, it can help you understand:

  • How your energy supplier works out your bills
  • Why some appliances use much more gas or electricity than others - and how much individual appliances use
  • Why you should turn appliances off at the wall to save energy costs, and not just leave them on standby

You can then use that information to help you monitor your gas and electricity use, cut costs and lower your bills.

It’s also a good way to make really accurate comparisons if you’re thinking of switching gas or electricity provider, or want to check you’re getting a good deal, because you can look at the exact cost of electricity per kWh – and then do the same for gas.

So what exactly is a kilowatt hour?

A kilowatt hour (kWh) is a measure of how much energy you’re using.

It doesn’t mean the number of kilowatts you’re using per hour. It is simply a unit of measurement that equals the amount of energy you would use if you kept a 1,000 watt appliance running for an hour:

So if you switched on a 100 watt light bulb, it would take 10 hours to rack up 1 kWh of energy.

Or a 2,000 watt appliance would use 1 kWh in just half an hour.

While a 50 watt item could stay on for 20 hours before it used 1 kWh.


What else takes around 1 kilowatt hour?

It’s hard to be precise, because the similar appliances can have very different wattages, but here are some rough examples of 1 kWh:

  • Using a 10,000 watt electric shower for six minutes
  • Keeping an immersion heater (3,000 watts) on for 20 minutes
  • Cooking in a 2,000 watt oven for half an hour
  • An hour’s ironing with a 1,000 watt iron or 45 minutes with a 1,500 watt iron
  • Less than an hour using a dishwasher (1,000 - 1,500 watts)
  • Around three hours watching a plasma TV (280 - 450 watts)
  • Keeping a fridge-freezer (200 - 400 watts) on for about three hours
  • Keeping an electric blanket (130 - 200 watts) on all night
  • Using a laptop (20 - 50 watts) all day
  • Keeping a broadband router (7 - 10 watts) on for five days

What’s the difference between kWh and kW?

kW stands for kilowatt. A kilowatt is simply 1,000 watts, which is a measure of power. So, for example, the 10,000 watt electric shower in the top bullet point above could also be called a 10 kilowatt shower.

A kilowatt hour (kWh) is a measure of energy.

So a 1,000 watt drill needs 1,000 watts (1 kW) of power to make it work, and uses 1 kWh of energy in an hour.

That’s why, if you leave a TV or computer on standby, it is still using power and creating a kWh cost on your energy bill.

How many kilowatt hours should I be using each year?

That depends on the size of your home, the number of people in your family, and whether you spend a lot of time out at work, or most of your time at home.

According to energy industry figures:

  • If you live alone in a small home and are out at work full time, you might use 2,000 kWh of electricity a year and 9,000 kWh of gas

  • A small family who live in a three-bedroom house and are in full-time work and education might use 3,200 kWh of electricity and 13,500 kWh of gas

  • Four or five students sitting around all day in a large four-bedroom house could rack up about 4,900 kWh of electricity and 19,000 kWh of gas

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Can I use kWh to compare energy costs?

If you’re checking energy prices on a comparison site, you can get a much more accurate idea by entering your kWh use. You’ll find it on your bills or annual statement.

Be sure to enter the right timescale as well. If you enter 3,000 kWh a month when you actually use 3,000 kWh a year, you might be shocked by the prices you’re quoted.

How can I cut my energy costs?

A. Use less energy

The best way to use fewer kWh and reduce your bills is to make sure your home and all your electrical appliances are working as efficiently as possible.

If you insulate your roof and walls, improve your heating system and generally be quite careful, you can save around £300 a year. You’ll also cut your home’s carbon dioxide (CO2) emissions by around 1.5 tonnes – so you’re helping the planet, too.

Here are ten ways to become more energy efficient:

  • When you boil a kettle, only use as much water as you need – this will cut your annual kWh levels
  • Turn appliances off at the wall – don’t leave them on standby
  • Use energy-saving light bulbs as they are a lower wattage and use fewer kWh
  • Defrost your freezer regularly
  • Fill that cavity! Cavity wall insulation can cut around £115 off your heating bill each year
  • Get draught excluders for outside doors, windows and letterboxes
  • Replace all your old windows with double glazing – it could save you around £135 each year
  • If your boiler’s more than 15 years old, look into replacing it with a new A-rated condensing boiler
  • Slip an insulating jacket on your hot water tank – you could save around £35 a year
  • When using your washing machine, never set it higher than 30˚


B. Switch providers

No matter which energy company you’re currently with, it’s always worth checking the market regularly to see if you could save money by switching.

At OVO, we know that price matters – that’s why we keep our costs down, to help you save. You'll also get our 3% OVO interest reward on any credit in your account.

See how your current provider matches up next to our range of energy plans – you can compare energy prices for our electricity, gas and dual fuel plans by looking at the cost of electricity per kWh and then the kWh cost for gas. They’re based on a medium user, paying by Direct Debit, averaged across all UK regions. It’s the quick and easy way to compare utility prices.

Remember, you can get a more accurate comparison by entering your actual kWh figures for gas and electricity.

To find out how much electricity an average UK home uses, and how your home compares, read our new guide. 

Check our range of plans and see how much you could save now.

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