What does kilowatt hour (kWh) mean on your bill?

If you know what a kWh is, it can help you understand how your energy supplier works out your bills and how much energy you're actually using.

Disclaimer: The information on this page was last updated on 23/12/2022, 13:30:22

‘kWh’ (kilowatt-hour) is one of the most common terms you’ll see when it comes to managing your energy usage. But what does it mean and how does it affect your gas and electricity bills?

What is a kilowatt-hour?

A kilowatt-hour (kWh) is one of the many units we can use to measure our electricity usage.

They’re based on watts (W) and kilowatts (kW) (1,000 watts) which measures the rate at which electricity is being used in a period of time.

A kilowatt-hour uses this to measure the amount of electricity being used over time in kW. It isn’t always exactly a measure of how many kilowatts are being used per hour, but the amount of electricity you would use if you kept it running for an hour.

How much is 1kWh?

1 kWh is 1,000Wh. It’s also equivalent to 860 calories (kcal)!

In practical terms, 1kWh is roughly the same as:

  • Using the oven for half an hour
  • Ironing for an hour
  • Watching TV for 5 hours
  • Keeping a 50W lightbulb on all day (20 hours)
  • Using a laptop all day
  • Boiling the kettle 10 times
  • Keeping a broadband router on for 5 days
  • Running the dishwasher for an hour

How much does a kWh cost in the UK?

How much you pay per kilowatt-hour depends on your electricity provider and tariff. Different tariffs have different rates, determined by wholesale prices, competitor prices, location, and Ofgem price caps.

According to The Energy Saving Trust, the average kWh cost in the UK is around 16p, however, you could expect to pay anything between 12p and 25p. You can find out how much each kilowatt-hour is costing you by looking at your bill or tariff information, but here are some of the prices from other providers’ fixed tariffs.

Provider Price per kWh
British Gas 20.769p
EDF Energy 18.4p
EON 18.9p
Scottish Power 20.32p

*Based on a London postcode

Working out how much electricity you’re using

When you submit your meter readings, you’re actually telling your provider how many kWh you’ve used. The number you submit is how many kWh has gone through your meter since it was installed, so to find out how much energy you’ve used, simply compare two readings. The difference between the readings is how much you’ve used in that time.

For example, if last month’s meter reading was 10250 and this month’s reading is 10500, you will have used 250kWh.

If you have a smart meter, you can view your usage in real-time or view it over time. Many providers also allow you to compare your usage against previous periods to see how your usage has changed. You can usually find these through your online account or the app.

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How to calculate kWh

If you want to calculate the kWh for a specific appliance, simply multiply its wattage by the number of hours you use it and divide that number by 1000.

kilowatt-hour = (watts x time)/1000

For example, if a 60W lightbulb is on for 5 hours, you would do 60W x 5hrs = 300/1000 = 0.3kWh.

How to calculate your gas usage in kilowatt-hours

Gas usage is measured in ‘gas units’ so is worked out a little differently. While you don’t have to convert gas units to kWh, you might see your usage converted to kilowatt-hours on your gas bill so it’s useful to know when looking into how much you’re spending on your gas bill.

To work out your gas usage in kWh, you’ll first have to find out if you have an imperial or metric meter.

If you have an imperial meter, your gas usage will be measured in hundreds of cubic feet (100ft cubed). To convert gas units to kWh, you should:

  1. Take a meter reading and subtract this reading from the previous reading to work out how manu gas units have been used
  2. Convert from imperial to metric by multiplying it by 2.83
  3. Multiply by Volume Correction Factor (VCF) which is 1.02264
  4. Multiply by calorific value, which is 40
  5. Divide by the kWh conversion factor, which is 3.6

The final answer will be your usage in kWh.

If you have a metric gas meter, your gas usage will be measured in cubic meters. To convert gas units to kWh, you should:

  1. Take a meter reading and subtract this reading from the previous reading to work out how much gas has been used
  2. Multiply by Volume Correction Factor (VCF) which is 1.02264
  3. Multiply by calorific value, which is 40
  4. Divide by the kWh conversion factor, which is 3.6

The final answer will be your gas usage in kWh.

How many kWh should I be using?

There’s no set answer to this question, it all depends on your individual circumstances. However, Ofgem collects data every year to work out how much energy the average household uses for you to compare.

Low Medium High
Household size 1-2 bedrooms 2-3 bedrooms 4+ bedrooms
Electricity (profile class 01) 1800kWh 2900kWh 4300kWh
Electricity (profile class 02) 2400kWh 4200kWh 4300kWh
Gas 800kWh 12000kWh 17000kWh

Using fewer kilowatt-hours and saving money

If you’re using more energy than you’d like, there are all kinds of different ways to cut back on your usage and spending.

Around the house

  • Turn lights off when you leave the room - This is one of the easiest ways you can save energy. Switching off lights you don’t need could save you up to £90 per year!
  • Turn down the thermostat - Every degree you turn your thermostat down by could save you an average of £80 per year! Would you notice a 1-degree difference?
  • Keep a closer eye on your usage - The more aware you are of your energy usage, the more likely you’ll notice when and where you’re using more than you should. Having a smart meter installed is a great way to keep track of your real-time and overall energy usage.
  • Switch to LED lightbulbs - LED lightbulbs use a lot less energy than halogen bulbs. They’re also brighter and have a longer lifespan (up to 20,000 hours longer!).

When you're cleaning

  • Air dry your clothes - Tumble-dryers are energy guzzlers. In Britain, we spend over £375 million tumble-drying our clothes over the SUMMER.
  • Take shorter, colder showers - Showers tend to use less energy than having a bath, but if it’s running for too long, you could be increasing your energy usage instead. You can also opt for a low-flow showerhead to cut back even more.
  • Wash clothes at a lower temperature - Washing your clothes at 30C won’t just use less energy, it will also make them last longer.
  • Defrost your fridge and freezer regularly - The more ice that builds up in your fridge and freezer, the harder they have to work and the more energy needed to keep your food at the right temperature.

Using your appliances

  • Unplug electronics that aren’t being used - Even if they’re not being used, sometimes electricity is still passing through your electronics. Even just the power or charging light being on is increasing your energy usage.
  • Upgrade your appliances - Newer appliances are much more energy-efficient than older ones. The more energy-efficient your appliances, the less energy they’re using and the more money you’re saving in the long run.
  • Try and keep the heating off - Try and hold off putting the heating on. More clothes, blankets, and even a small electric heater can help heat your home for less.

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