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Electricity companies bill customers for the electrical energy they use.

A joule is much too small a unit of energy and so the electricity companies use another unit of energy called the kilowatt-hour, kWh.

One unit of electrical energy is one kilowatt-hour, or 1 kWh.

Electricity meters

Domestic electricity meters, similar to those above, measure the number of kilowatt-hours of electrical energy used in a home or other building.

The more kilowatt-hours (or units) used, the greater the cost.

The cost of the electricity used is calculated using this equation:

Total cost = energy in kWh × cost per unit

The cost per unit is set by the electricity company, for example 14.78 p per kWh.

This means that each unit, or kilowatt-hour, of electricity costs 14.87 p.

An electricity bill has two important numbers: present meter reading and previous meter reading.

The number of units used is the difference between these two readings.

Present reading = 40745 kWh

Previous reading = 39990 kWh

Energy in kWh = present meter reading - previous meter reading

= 40745 – 39990

= 755 kWh

Total cost = energy in kWh × cost per unit

= 755 x 14.78 p

= 11159 p

The cost of electricity used is £111.59

In 2019, the average household electricity bill for the year cost around £590, in comparison to 2013 when it cost around £650 - this could be caused by many household items becoming more energy efficient.

Ways of reducing electricity bills:

• Use energy efficient light bulbs such as LED bulbs.
• Switch off and unplug devices on stand-by.
• Switch off and unplug chargers when not in use.
• If you are replacing an electrical appliance such as a tumble dryer, kettle or hair dryer choose an energy efficient model.
• Minimize the time spent in an electric shower.
• If possible, hang washing out to dry rather than use a tumble dryer.