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Glossary of electrical terms

Find out what all the unit measurements on your bill mean

Volt (V) = a unit of electrical voltage

A volt is the electrical force required to push current through an electrical circuit. Most domestic homes in Ireland are supplied at a nominal voltage of 230V (single phase). Most businesses are supplied at a nominal voltage of 400V (three phase), which is frequently referred to as 'Low Voltage'.

Kilovolt (kV) = 1000 volts

This is the term normally used for medium and high voltages, e.g. 20 kV = 20,000 volts.

Amp (A) = a unit of electric current

An amp is the measurement of current flowing in an electrical circuit. Its full name is an 'ampere'.

Watt (W) = a unit of electric power

A watt is the unit of measurement of 'active/real' power. The power used in a basic electrical circuit is the volts multiplied by the amps.

1 volt passing a current of 1 amp through a basic circuit means that 1 watt of electric power is consumed.

Kilowatt (kW) = 1000 watts (W)

A kW is the term normally used for 'active/real' electric power, sometimes referred to as 'Demand' or 'Load'.
Electric power is made up of two components:
Active/real power (kW)
Reactive/wattless power (kVAr)
When these are combined they are referred to as the 'apparent' power (kVA).

Kilowatt hour (kWh) = 1000 watts for 1 hour

This is the basic unit of electricity consumption and refers to the real/active electric load (kW) used over time.
In simple terms, 1 kWh is the amount of energy consumed by an electrical device (e.g. an electric heater) that is rated at 1kW (1000 watts) for 1 hour. A further example is ten 100-watt light bulbs used for 1 hour.
A kWh is the basic unit of electricity consumption used by Electric Ireland to bill customers for the active/real power they use.
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