Appliance running costs

All electrical appliances have 'ratings' on them - their 'wattage'. You will find this on a small plate or written somewhere in the appliance itself. In order to to able to use these power ratings to calculate the amount of electricity used by each appliance, we also need to know the length of time that each appliance is used.

To work out how much electricity an appliance uses, you must have three values:

• The power rating or wattage of the appliance. This is found on the appliance.·
• The time the appliance is on for.
• The cost per unit.

You can work out the running costs of various electrical appliances by using the following formula:

Rating in Watts ÷ 1000 x Time in minutes ÷ 60 = Amount of electricity used in kWh.

Then:

kWh x Cost per unit = Cost of electricity used

(If the wattage is expressed in kilowatts simply use the number given. Similary if the time is expressed in hours, use the number given.)

Calculations below are based on the Home Energy Tariff, with cost per unit of electricity = 14.31 pence & VAT = 5%

EXAMPLE: 100 watt light bulb on for 24 hours

(100 ÷ 1000) × (1440 mins ÷ 60) = 2.4 kWh or units used

(2.4 kWh × 14.31) = 34p + VAT = 36p

This means that it costs 36p to use a 100 Watt light bulb for 24 hours.

EXAMPLE: Equivalent energy saving light bulb (20 Watts) for 24 hours

(20 ¸ 1000) × (1440 mins ÷ 60) = 0.48 kWh or units used

(0.48 kWh × 14.31) = 7p + VAT = 7.5p

This means that it costs just 7.5p to use an equivalent low energy light bulb for 24 hours.

As you can see using a low energy saving light bulb in place of an ordinary light bulb will save you 28.5 pence every 24hour period your light is on.

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