kWh: What is a Kilowatt Hour?

Your need-to-know guide to understanding kilowatt hour

Whenever you switch on the lights in a room, power up your appliances or heat your home, you're using energy to do this.

Think of the energy that you are using as a product that you pay your gas or electricity company to supply to you. There needs to be a system in place so that your energy provider can price the energy that you use, ensuring it is charged for fairly.

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It's not possible to price energy by measuring how many times you use an appliance, such as the number of times you boil a kettle, because some kettles will be more efficient than others. Instead, the energy used to boil your kettle is measured into a unit called a kilowatt-hour (kWh), and each kWh unit is priced.

Understanding kWh

Your electricity supplier uses kWh to determine how much energy you have used and to calculate your bill.

It's important to have a clear understanding of how many kWh you use on a normal day because, armed with this information, you can discover new ways to improve the energy efficiency in your home.

Check through your energy bills and consider how you and your family use household appliances, lighting and heating. Using these observations, you can start to work out how much electricity each of your appliances consumes, how much they cost to run, and therefore, how to cut down your bills.

By becoming more informed about your behaviour patterns and average energy consumption, you'll recognise just how much money being savvy with your gas or electricity usage could save you.

How much energy is in one kilowatt-hour

One kilowatt-hour, or a single kWh, is one thousand watts of electricity used during one hour. It's a standard measurement of energy.

Each kWh represents one unit of energy. Your gas or electricity supplier will charge you per unit of energy you use, and they calculate this with kWh to work out your bill.

How much energy your household will use

The amount of energy you will use in your house depends on a variety of factors, such as the:

  • size of your home,
  • number of residents,
  • percentage of time spent there,
  • energy efficiency.

To put this measurement into perspective, you can review the average estimates of energy consumption reported by the energy industry:

Small households of just one or two people who use a modest amount of energy will consume around:

  • 2,000 kWh per year of electricity
  • 9,000 kWh per year of gas

Medium households, such as a small family living in a three-bedroom home, will consume around:

  • 3,200 kWh per year of electricity
  • 13,500 kWh per year of gas
  • Large households with occupants who spend a lot of time at home and include four or five bedrooms will consume around:

    • 4,900 kWh per year of electricity
    • 19,000 kWh per year of gas

    How far 1 kWh can go

    The exact amount of energy each household appliance uses will depend on the type of appliance, its manufacturer and its energy efficiency.

    Similar appliances can have varying wattages, so the power each appliance uses can vary from make to make. However, there are rough figures that you can use to estimate how far one unit of energy goes.

    For every kWh, you can power roughly:

    • 6 minutes using an electric shower,
    • 20 minutes using an immersion heater,
    • 30 minutes cooking in an oven,
    • 10 boils of a kettle,
    • 1 washing machine cycle,
    • 1 hour of ironing,
    • 3 hours of television,
    • 3 hours of running a fridge-freezer,
    • 4 hours of desktop computer use,
    • 48 hours of laptop computer use,
    • 1 night warming an electric blanket,
    • 5 days of connecting your internet.

    How much you will pay per kWh

    What you pay for each unit of energy you use depends entirely on the electricity deal or gas deal you sign up for.

    Each energy plan comes with its own pricing. Gas or electricity deals on fixed-rate tariffs will have a set rate for each kWh used, whereas the rates for each kWh you use on flexible tariffs will reflect the energy market.

    To find the best possible deals, so you can heat, light and power your home at affordable rates, it's a good idea to compare gas and electricity tariffs from a range of suppliers.

    Using Utility Saving Expert's online comparison technology, you can instantly compare a huge range of deals. The results are tailored to suit you, based on your location and your typical household energy consumption.

    Some plans, such as fixed-price deals, will allow you to fix your energy costs for between one and four years. Others, like Economy 7 tariffs, will offer two prices, including more affordable rates for using energy during off-peak hours.

    When using the comparison site, add some details from a past energy bill. This ensures we can generate accurate estimates for how much you could save if you switch to each deal we show.

    You'll be able to examine the costs of energy per kWh from each supplier and decide which choice would be best for your home.

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    The difference between kW and kWh

    A kilowatt, or kW, is equal to 1,000 watts. Using watts and kilowatts helps us to record and communicate how powerful any given appliance is, such as an oven, shower or washing machine. Rather than a measure of energy, this is a measure of power.

    To communicate a measurement of energy, you need to work in kilowatt-hours (kWh). This tells us precisely how many kilowatts is required to power an appliance for any given time.

    Let's say an appliance uses 1,000 watts, or 1 kW, of power to work. It is left running for approximately one hour. That's one kilowatt of energy used in an hour, which is equal to 1 kWh. If you used that same appliance for four hours, you will have used 4 kWh of energy.

    Knowing how to differentiate between kW and kWh will help you dig into your energy bills and discover which appliances are using the most energy.

    Each household appliance will also come with a power rating, usually labelled on the back or bottom of the appliance or contained on its packaging. The power rating tells you how much electricity the appliance needs to work, and should also be available online, so it's worth checking the manufacturer's website to find out the rating if you can't find this information elsewhere.

    Whilst you might lean towards household utilities using lower wattages, it's worth doing your research before you commit, because it can be more complex than it seems. Some appliances that require more power to function are also more efficient than low watt equivalents. This means that, in some cases, higher wattages can translate to less energy consumption overall.

    Similarly, some energy-efficient appliances that run at a much lower wattage for longer periods will cost less than high power alternatives. There is no simple, definite rule that applies to all of your utilities. However, aiming for energy efficiency wherever possible will help you to lower your energy consumption and reduce your bills.

    How to reduce your energy bills

    There are a few simple ways to pay less on your energy bills. These include:

    1. improving the energy efficiency of your home,
    2. installing higher quality, more efficient appliances, and
    3. comparing and switching gas or electricity supplier.

    Energy-efficient home improvements make each kWh go further

    Reduce your bills with DIY home improvements that ensure your home doesn't lose much of the energy you generate. Consider adding:

    • an A-rated condensing boiler,
    • an insulating jacket for your hot water tank,
    • cavity wall insulation,
    • double glazing for windows,
    • draught excluders for letterboxes and doors.

    Choosing appliances that consume less energy lowers your bills

    If all your appliances are working as efficiently as possible, you will use less energy and pay less each month on your electricity bills. Consider:

    • defrosting your freezer more often,
    • installing energy-saving light bulbs,
    • switching off appliances,
    • using less water when you boil your kettle,
    • washing clothes at 30 degrees.

    Deals with low kWh unit rates offer better value for money

    One of the quickest and simplest ways to trim down your energy bills is to compare better deals and switch to a cheaper gas or electricity tariff. You can do this for free using the independent and impartial comparison technology at

    When comparing energy prices, check a past energy bill to find your average kWh usage and check the timescales, such as whether this is per month or year. Inputting correct data ensures you'll generate a precise comparison with accurate estimates for potential savings.

    Browse through the results that are generated, which will show the cheapest options at the top. Along with the quotes, you'll also be able to read some important information about the energy suppliers and how their contracts work, such as the type of tariff, whether they will charge exit fees, and how long the contract will last. You'll also be shown a provider rating to give you some insight into each energy company's reputation.

    Once you have used all of the information provided to make your choice, confirm you'd like to switch, then input a few important details and the rest of the process will be handled for you. You can do all of this from Utility Saving Expert's website, which is accredited by Ofgem and guaranteed to find you the cheapest deals.