A guide to kWh

Last updated: 28 January 2021

In this guide you’ll get answers to the following questions:

  • kWh: why should I care about it?

  • What is kWh?

  • Is there a difference between kW and kWh?

  • How do I convert kW to kWh?

  • What is the average kWh cost?

  • Where can I find my kWh information?

  • How to switch using kWh figures

kWh: why should I care about it?

Even if you’ve never stopped to think about where your electricity comes from, understanding how it’s measured and charged can help you reduce your energy bills or find a better deal. Read on to discover all you need to know about kWh and the cost of electricity.

What is kWh?

A kilowatt-hour or kWh is a unit of measurement designed to track electricity consumption on an hour-by-hour basis. One kilowatt is the equivalent of 1,000 watts and is a simple means for your energy supplier to both measure how much energy your household consumes over a certain period and charge you for its usage. Anything plugged into an electricity socket consumes energy, and different appliances use different amounts of electricity depending on both their type and energy requirements, so your use will vary correspondingly.

To help put kWh into perspective and understand how much it represents, the following examples all roughly use a single kWh of electricity:

  • Ironing clothes for 22 minutes

  • Running one full washing machine or dishwasher cycle

  • Bringing your kettle to the boil ten times

  • Using a desktop computer for four hours

Average household use varies according to how many occupants there are in the property, how much time they spend at home, and what type of appliances they use. Ofgem published Typical Domestic Consumption Values (TDCV) in 2017 to use as a general reference. These are used as an industry standard to showcase how much gas and electricity the typical domestic consumer uses every year – the current figures for 2020 are: 

Household sizeGas TDCV (kWh)Electricity: Profile Class 1 TDCV (kWh) Electricity: Profile Class 2 TDCV (kWh)
Small (1-2 people) 8,000 1,800 2,400
Medium (3-4) 12,0002,900 4,200
Large (5+) 17,0004,300 7,100

Profile Class 1 is a typical single-rate tariff. Profile Class 2 mostly covers multi-rate tariffs and other complex rates

These are just rough estimates, however, as every household is different. It does give you some idea of where your own household might fit in, which is helpful if you’re comparing energy tariffs and rates.

Is there a difference between a kW and a kWh?

You’ll often see both kW (kilowatt) and kWh mentioned with regards to electricity. The difference is that kW refers solely to kilowatts, the unit of power a device uses to operate at any single point in time. A kWh is used to represent how much energy is actually used.

One way to look at this is to view an electric appliance or device as a car. In this analogy, kW refers to its current speed (say 40 mph), while kWh indicates the distance you’ve actually travelled (such as 30 miles). The more miles you cover, the higher your fuel costs – just as your energy bills increase the more kilowatt-hours you use.

For example, if your dishwasher has a power rating of one kW and you run it for one hour, it will have consumed 1 kWh of energy, whereas a 10-watt light bulb would need to be switched on for 100 hours to consume the same amount of electricity. 

How do I convert kW to kWh?

Knowing an electrical device’s power rating can help you stick to a budget, along with the electricity prices per kWh. These figures will give you some indication of how much energy you’re using. All appliances come with a designated power rating. While this is often clearly labelled right on the appliance or packaging, in some cases you’ll need to look at the manufacturer’s website or online product listing. 

The power rating is usually given in watts, which you’ll need to convert to a kilowatt unit by dividing the wattage by 1,000. For example, an appliance with a 500 W power rating would have a kW rating of 0.5. To convert this kW number to KWh, simply multiply the kW rating by the length of time it’s used. In the example of the appliance with a 0.5 kW rating, if you run it for 24 hours, it would use 12 kWh per day, or 0.5 kW per hour. 

Why do you need to know this? Because it enables you to calculate just how much money you’re spending, using electricity prices per kWh. In the above case of a device that operates with 12 kWh per day, if your electricity price per kWh is 10p you would be spending £1.20 per day just on this appliance alone – or £36 per month. By shutting it off for even eight hours while you’re at work, you’ll save £12 per month!

What is the average kWh cost?

As you’ll discover when comparing energy prices, there’s no standard price for electricity within the UK. Suppliers are free to set their own prices dependent on market rates and additional factors. The kWh cost will vary depending on your postcode and tariff. To find the best rate, you’ll want to shop around using a comparison website. It’s still helpful to keep the average prices in mind to see how your household compares. 

The Energy Saving Trust calculates energy prices using a national average kWh cost, which is currently calculated at 16.36p per kilowatt-hour (as of April 2020). While this is the average amount you might expect to pay, keep in mind that this applies to electricity rather than gas. Your actual rates will depend on your region, the plan you’re on, and your payment method (such as direct debit). 

Some customers may also have plans with savings dependent on the time of day you consume energy, like Economy 7 tariffs. These offer a separate kWh price for energy used during the daylight hours and energy consumed overnight. If you’re not sure what you’re paying, this information should be clearly displayed on your energy bill. 

Why do I need to know my kWh usage? 

Your kWh usage is the best way to track your household energy use. Although it’s often skimmed over when you’re reading your utility bill, this bit of information is one of the most useful pieces of data. This is particularly true if you want to gain control of your household’s energy consumption, as you can see just how much energy you’re using, and what you’re paying for it. 

When a bill is higher than expected, examine your kWh electricity and gas usage to find out which fuel is using more energy. Identifying which specific appliance might be leading to higher fuel bills can be tricky, which is where a smart meter comes in handy, because it can let you see when jumps in energy usage occur, helping you tie that usage to specific energy-sapping devices. These are the areas you can then focus on to boost efficiency and slash bills. It’s a handy reminder to do simple things like turn off lights when you leave the room and wait to run the dishwasher until it holds a full load. Even the little things add up – a mobile phone left charging overnight, or a desktop computer left on standby mode when not in use. 

How can I find my kWh energy information?

Energy bills contain far more information than a simple statement of what you owe. Whether you’re pulling up a monthly bill or annual statement, be sure to have a look at the usage section. This should provide a detailed breakdown of how many kWh you’ve used during the billing period, along with the rate and your most recent meter readings. This applies to kWh electricity bills. For gas, sometimes the energy supplier will show your usage information in gas units rather than kWh energy units. If this is the case, follow gov.uk’s advice to convert it into kWh. 

How to switch using kWh figures 

A final reason to keep track of your kWh consumption is that it gives you ammunition for switching energy suppliers. When you visit a comparison website, you’ll be asked for some basic information, including your postcode. Having your kWh energy use information close to hand ensures that you’ll get a more accurate quote, based not just on estimations but on your actual usage. This means you’ll gain access to customised tariffs that best apply to your home, potentially saving you more money in the process.

Are there any other charges on my electricity bill?

Yes, you’ll also pay a daily standing charge to cover other aspects of supplying and administering your electricity supply.  

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Published on Wed 28 Oct 2020 10.30 GMT