Last edited 30 Dec 2020

Main author

ECA Institute / association Website

Electrical consumption

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Electrical energy supplied to or generated within a building is used to serve a number of purposes within the building, where it is usually converted into another form of energy.

These may include:

The rate at which energy is used is termed electrical power, usually measured in watts.

The accumulation of electrical energy that has been used in any given time, is termed the electrical consumption, or electrical use and is very often metered for billing purposes.

Electrical consumption is most often measured and compared by reference to the term Kilowatt hour. In its most basic form, this is the amount of energy used by a resistive load of 1000 watts (1kW) running for 1 hour. This quantity of energy can be equated to, say, running a 1kW electric heater continuously for 1 hour, and the amount of energy used by this would be 1kWh or ‘1 unit’ of electricity.

Equally, a 100W filament lamp (0.1kW) running for 10 hours would consume 1kWh of electrical energy.

Many smaller electrical installations are billed for their consumption based on the number of kWh used over a given time period, plus a ‘standing charge’ which covers supplier and distributor costs.

Larger consumers of electrical energy will be billed based on a more complex sets of conditions – taking into account the power factor of the connected load, maximum demand at any given time, time of day, season, as well as system use charges and other overheads borne by the supplier and distributor.

Details of billing arrangements are set out in energy companies’ terms and conditions and are known as tariffs.


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