What is a kWh and how much does electricity cost per kWh?

13 May 2024 | 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. Also, the figures included in this article were correct at the time of publication, May 2024, but may now be incorrect due to the changes in the cost of energy. 

When you look at prices for energy plans and tariffs, or at your energy bills, you’ll see electricity and gas measured in kWh. Understanding kWh, or kilowatt hours, is a big part of making sense of your bill, reducing your carbon footprint, and keeping an eye on your energy costs.

If you know what a kilowatt hour is (and how much it costs), it’s much easier to 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

You can then use that information to help you keep tabs on your gas and electricity use, and cut the cost of your bills.

It’s also a good way to make sure you’re getting a good deal if you’re thinking of switching gas or electricity provider. By looking at the exact cost of electricity or gas per kWh, you can compare different tariffs like for like.

What exactly is a kilowatt hour or kWh?

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

Despite the name, it doesn’t mean the number of kilowatts you’re using per hour. It’s a unit of measurement. 1 kilowatt hour is the amount of energy you’d use if you kept a 1,000 watt appliance running for an hour. 

But different appliances use different amounts of energy – an alarm clock uses a lot less power than an electric kettle. Here are a few examples:

  • A 50 watt alarm clock would take 20 hours to use 1 kWh
  • A 100 watt light bulb would take 10 hours to rack up 1 kWh
  • A 2,000 watt dishwasher would use 1 kWh in just half an hour

So what can 1 kWh power?

It varies a lot between appliances – some are more energy-efficient than others. Here are some (estimated!) examples of what might use 1 kWh:

  • Running an electric shower (10,000 watts) for 6 minutes
  • Keeping an immersion heater (3,000 watts) on for 20 minutes
  • Cooking in an oven (2,000 watts) for 30 minutes
  • Using an iron (1,000 watts) for 60 minutes
  • Running a dishwasher (1,000-1,500 watts) for less than an hour
  • Keeping a fridge-freezer (200-400 watts) on for about three hours
  • Watching a 42” LED TV (80 watts) for 12 and a half 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

Some appliances still use energy in standby mode. If you leave a TV or computer on standby, it’s still using a small amount of power and adding kWh to your energy bill.

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What’s the difference between a kW and a kWh?

kW stands for kilowatt, which is a measure of how much power an appliance needs to run. A kilowatt is 1,000 watts. For example, a 1,000 watt vacuum cleaner is also a 1 kW vacuum cleaner.

kWh stands for kilowatt hour (kWh) – it’s the way we measure energy in the home. 1 kilowatt hour is the amount of energy it takes to run a 1,000 watt (or 1kWh) appliance for 1 hour. 

How much does 1 kWh of electricity cost?

The price of energy depends on the market conditions and price cap at any given time. For this example, let’s say that the price for 1 kWh of standard rate electricity is 28p.

Let’s say you have a 1,000 watt electric heater – also known as a 1kW electric heater. Now imagine you leave that heater on for 3 hours every day. 

To work out the kWh cost of running your heater for 3 hours a day, you would multiply the kW rating of the appliance by the hours you’re using it and by the electricity cost in pounds and pence

So for your electric heater, that would look like:

1kW x 3 hours x 0.28p electricity cost per kWh = £0.84p a day

All of your appliances use energy in this same way. You’ll use some of them for just a few minutes a day (like your kettle), while others are on 24/7 (like your fridge). But they’re all using electricity.

If you’d like to learn more about how much you’re spending on heating, here’s a guide to understanding your heating costs.

Want to see how much energy you’re using, but don’t fancy doing the maths? It’s a good idea to get a smart meter. Smart meters track your energy use in pounds and pence – so you know exactly how much you’re spending on energy at any time.

What determines my electricity cost per kWh on my energy bill?

When it comes to your bill, the price you pay is based on: 

All these factors could affect your unit rate. That’s the amount you’re charged per kWh of energy you use. If you’re on a fixed rate plan, this will be the same for the length of your contract. If you’re on a variable plan, this price could go up or down.

There’s also the standing charge. This is a fee charged every day, no matter how much energy you use. It’s used to pay for providing energy to your property via the National Grid, and other costs your supplier covers.

Whenever you’re looking at an energy plan, make sure you check both the unit rate and the standing charge to get a clear picture of how much it’ll cost overall. This is much easier if you also have a rough idea of your average energy use.

Energy suppliers base their prices on the cost of wholesale energy. As an energy supplier, we buy wholesale energy, which we then sell to our customers. The price per kWh of that wholesale energy is based on lots of different factors.

How many kilowatt hours should I be using each year?

How many kWh you’ll use annually depends on the size of your home, the number of people in your family, and whether you spend a lot of 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 3-bedroom house and are in full-time work and education might use 3,200 kWh of electricity and 13,500 kWh of gas
  • 4 or 5 students who spend most of the day at home in a large 4-bedroom house could use about 4,900 kWh of electricity and 19,000 kWh of gas

You can find out more in our blog post about average electricity use in the UK.

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 of how much you’ll pay by entering your energy use in kWh. You’ll find it on your bills or annual statement.

Don’t forget to check you’re entering the right time period. Some sites will look at cost over a month, while others will look at cost over a whole year.

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Become an energy-saving expert

Ready to get serious about cutting your energy use? Now that you know how to work out how much 1 kWh costs, you can work out how much you’re spending on energy throughout your home.

Work out what you’re spending on energy

It’s worth working out what the different appliances in your home cost to run. Let’s take watching TV, for example:

  • Imagine you watch TV for 6 hours a day
  • Your TV has a 200 watt power rating, which is 0.2 kilowatts
  • You multiply your TV’s kilowatt power rating (0.2 kW) by the time you spend watching it (6 hours)
  • So that’s 0.2kW x 6 hours = 1.2 kilowatt hours or kWh
  • Your TV uses 1.2 kWh per day, on average

Now you know how many kWh your TV uses, you can find out how much it costs. Here’s how you’d work it out:

  • Take the 1.2 kWh for your daily TV usage
  • Multiply 1.2 kWh by your electricity price per kWh – we’re using 0.28p per kWh as an example
  • So that’s 1.2kWh x 0.28p = around 0.34p a day 
  • That adds up to £125 a year

It’s just an example, but it shows you how using your appliances at home can add up over time. Here are a few more estimated examples:

  • Shower: running a 7.5 kW shower for 10 minutes a day at 28p/kWh will cost 35p a day, or £127 a year
  • Microwave: using an 0.8 kW microwave for 10 minutes a day at 28p/kWh will cost 4p a day, or £14 a year
  • Dishwasher: using a 2.2kW dishwasher for a 60-minute cycle at 28p/kWh will cost 62p a day, or £226 a year
  • Space heater: running a 2kW space heater for 60 minutes a day at 28p/kWh will cost 56p a day, or £204 a year

Bigger appliances, particularly ones that use water or heat, tend to use the most electricity – so if you’re keen to cut your energy use, it’s best to start with those.

Find ways to save energy

Now you’ve got a solid knowledge of how kWs and kWhs work, you can look for opportunities to use energy more efficiently. 

  • Do you run the dishwasher when it’s only half full? Try waiting for a full load and use the eco setting.
  • Do you fill the kettle up completely when you’re only making 1 cup of tea? Just fill up with the water you need.
  • Do you leave the lights on when you leave the room? Start being strict about switching off.

They’re small tweaks, but they add up quickly.

What else can I do to save money on energy and cut my carbon footprint? 

At OVO, we’re all about helping you on the Path to Zero – one step is making your more home energy-efficient. It’s all part of our mission to make energy better for you, your wallet, and the planet.

Here are a few more tips on how to reduce your gas and electricity bills:

  • Draught-proof your gaps. Insulating your loft and double-glazing your windows makes a huge difference to your warmth, and your wallet. 
  • Get low-energy lightbulbs. They use 90% less energy than regular ones, and they last 10 times longer. Win-win! 
  • Switch off plugs at the wall. Idling appliances like TVs and laptops are costing you around £35 a year
  • Use your smart meter to track your energy use and spot ways to cut wasted energy. If you haven’t got one yet, how about getting one installed?
  • Download our app to get personalised insights that’ll help you use less energy.

Now that you know the difference between watts, kW, and kWh, you’ve taken your first step to becoming an energy saving expert – doing your bit to save energy, save money, and live more sustainably. Nice work. It’s an important step to take on the Path to Zero

Looking for more advice? Check out our Energy Experts service for energy efficiency advice that’s tailored for your home.

Take control of your energy use with a smart meter

By allowing you to track your energy use, smart meters can help you make small changes to waste less energy – cutting your bills and your carbon emissions. It’s a win-win.

You’ll also be ready to access our latest energy and money saving ideas – like Power Move and OVO Beyond

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