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What is a unit of electricity

Your electricity bill will show the electricity used in 'units', the price of each unit is also shown. Ever wondered what a 'unit' of electricity is or how long you can run an appliance for on one unit. The examples below will help you to understand just what a unit is and just how much it buys you in real terms!

One unit of electricity is exactly equal to 1000 Watts of power used for 1 hour. So to find out how much an appliance costs to run per hour do the following:

  • Look at the cost you pay per unit (unit cost) (this may be anywhere between 4p and 12p depending upon your supplier and any special discount schemes) you can get the exact amount per unit from your electricity bill.
  • Look on the appliance label and look for its power consumption in Watts or kW (1000's of watts). This is how many Watts the appliance uses. An appliance with a power consumption of 1kW would consume 1 kWh (1 kilowatt hour or unit of electricity) every sixty minutes.
  • Calculate the how much the appliance costs to run per hour with the simple power calculation below.

    unit cost x power consumption in watts divided by1000

    Example:
    A 100 Watt light on in a house paying 5p per unit would cost:

    5p x 100 / 1000 = .5p (half a pence) per hour to run.

Activity: Let's see just how much appliances use relative to each other. This will show you the approximate speed at which electricity is used by a 3kW tumble dryer; a 100 Watt light bulb; and a low-power bedside clock radio alarm. We have sped up the usage by a factor of approximately 100 times so you don't have to wait too long. Select the coin to start the sequence.

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