What is a kilowatt hour?

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You’ve probably heard of a kilowatt (kW) but what about a kilowatt hour (kWh)?

Knowing what a kilowatt hour is allows you to monitor how much energy you use and where you could save, to ultimately lower your monthly energy bill. It’s also useful to learn the formula to convert kW to kWh.

When you glance at a bill you might only notice the cost involved. But look closer and you will see your energy usage or the number of kilowatt hours you use a month in your home. This blog will help explain how it works and how you can save money.

Understanding a kilowatt hour (kWh).

A kilowatt hour (kWh) is a way to measure how much energy you’re using and it is what we charge you by. Every electrical appliance has a power rating - usually shown in watts (W) or kilowatts (kW) (1,000W = 1kW). This is the amount of electricity the appliance needs in order to work.

A good way to think of a kilowatt hour is the length of time different electrical appliances take to use one kilowatt. Put simply, if you were to run a 1000 Watt appliance at home continuously for one hour, it would consume 1kWh of electricity. A 500 watt appliance would need to run continuously for two hours to consume 1kWh, a 250 watt appliance for 4 hours, and so on.

Some things have a low wattage rating like a fridge-freezer (300 W) but because they are always on they use a lot of electricity. On the other hand, a kettle (3,000 W) needs a high amount of electricity but only for a short time.

Here are some regularly used items found in most homes and how quickly they reach one kilowatt hour:

What can 1 kilowatt hour power*?

  • Taking an electric shower for 6 minutes.
  • Cooking in an oven for 30 minutes.
  • Ironing for 60 minutes.
  • Keeping a fridge-freezer on for about three hours.
  • Watching a 42” LED TV for 12 and a half hours.
  • An electric blanket switched on overnight.
  • Using a laptop all day.

How much does one kWh of electricity cost?

There’s lots of factors including where you live and your supplier. For example, right now the price for 1 kWh of standard rate electricity is 34p for a customer with typical usage, paying by Direct Debit*.

Let’s take a 1,000 watt electric heater - also known as a 1kW electric heater. You leave that heater on for 3 hours every day. To calculate the cost of that you would multiply the kW rating of the appliance by the hours you’re using it and by the electricity price in pounds and pence.

So for your electric heater, it would look like:
1kW x 3 hours x £0.34 electricity cost per kWh = £1.02p

All of your appliances use energy in this same way. The costs between them will vary, you might use some of them for just a few minutes a day (like your kettle), whilst others are on 24/7 (like your fridge.) But they’re all using electricity for different periods of time.

Smart meters can do the maths for you.

It can get complex trying to work out the usage and cost of all the gadgets around your home, which is why many people choose to get a smart meter. It’s a great way to keep track of all your energy usage and calculate the costs in one place. You’ll see how much you are using and how much it is costing you in real time.

How many kWh does a house use per day?

The amount of kWh you use depends on a number of things:

The size of your home - bigger homes generally cost more to heat and use more electricity.
When your house was built - newer homes tend to be better insulated.
Number of people - more people means more hot water and electricity used.
The type, number and age of appliances - for example some freezers are more energy efficient than others.

According to Ofgem, the average UK household has 2.4 people living in it and uses 8 kWh of electricity and 33 kWh of gas respectively, per day**.

How to reduce your electricity bill.

Being energy-conscious is a great place to start.The better you understand your energy use or average kWh per day, the more you know where it’s being used and potentially wasted.

It starts with the simple things like turning off the lights as you leave a room, turning down the thermostat when out. Shorter showers, having a full dishwasher, switching off devices rather than having them on standby. There’s a whole range of energy saving tips you can use.

New energy efficient appliances.

If you're replacing a microwave, a dishwasher or thinking of a bigger TV, checking the kWh rating is one of the first things you should do. You’ll usually find a label with an energy rating from A (most energy efficient) to G (least energy efficient). Also details of the annual energy consumption (kWh per year). This allows you to compare products and consider the energy costs involved in using them.

Contact our Energy Specialists if you’re worried about the increase in energy bills.

Our Energy Specialists are here to help if you're concerned about the impact of the increase on your energy bills. If you're struggling to pay, please visit our help page to find out more about how we can support you. You can reach out to our Energy Specialists for personal advice on Facebook and Twitter.

Feel the Community power.
The E.ON Next Community is a space for customers just like you, sharing their experiences to offer a helping hand. Find support or suggest your own unique topics, plus get involved in discussions of all the latest news. Join the conversation now.​​​​​​​

* Rates are average and will vary by region, payment method and meter type. Contact your supplier for personalised information.
** Figures correct for Ofgem’s average energy usage in 2020. New energy usage calculations have been delayed due to the pandemic. New figures should be released in 2023. You can find more details on this announcement at Ofgem.


Blog: 14/11/22