Business Help

Glossary of electrical terms

Are you a little puzzled by all the unit measurements on your bill? Here's a rundown of what they mean and how they apply to you.

Volt (V) = a unit of electrical voltage

A volt is the electrical force required to push current through an electrical circuit.

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 term is normally used for medium and high voltage business customers.

Amp (A) = a unit of electric current

An amp is the measurement of current flowing in an electrical circuit.

Kilovolt-Amps (kVA) = 1000 volt-amps

This is a term used to describe the level of 'apparent' power imported or consumed by your business,
It is the basis of your Maximum Import Capacity (MIC) contract with NIE Networks.

Watt (W)

A watt is the unit of measurement of 'active/real' power.

For example, 1 volt passing a current of 1 amp through a basic circuit means your business uses 1 watt of electric power.

Kilowatt (kW) = 1000 watts (W)

A kW is the term used for 'active/real' electric power, it’s also known as 'Demand' or 'Load'.

Megawatt (MW) = 1000 kilowatts (kW)

A megawatt is sometimes used as a unit of measurement for large electric loads provided to business customers.

Kilowatt hour (kWh) = 1000 watts for 1 hour

1 kWh is the amount of energy consumed by an electrical device (e.g. an electric heater) rated at 1kW (1000 watts) for 1 hour.
On your Bill, you will see each 1 kWh used by your business as 1 unit.

Megawatt hour (MWh) = 1000 kilowatt hours (kWh):

MWhs are the measurement of energy used by large industrial businesses.

Wattless unit (kVArh) = 1000 reactive volt-amps per hour

A kVArh is the unit of measurement for 'reactive/wattless' power consumed.

Electric power is made up of…

  • 'active/real' power (kW)
  • 'reactive/wattless' power (kVAr).

Which equals the 'apparent' power (kVA).

Large motors require 'reactive/wattless' power to operate correctly. Your business can reduce/eliminate reactive power by fitting power factor correction equipment. Please discuss with your electrical contractor.

Wattless charges are recorded on a separate meter.

Power factor

This term describes the relationship between kW, kVAr, and kVA.

It is always 1 or less. For example, if your power factor equals 1, then the kW used is equal to the kVA.

If your power factor is less than 1, then you are using some wattless power on your premises. We will only charge you for wattless power when the power factor goes below 0.95.

Load factor

Load factor is the ratio of average electricity consumption to the peak consumption in a business premises during a specific period.

It shows whether the electricity used in your business is stable or has extreme peaks. The lower the load factor the more 'peaky' the loads. A very poor load factor would be less than 20%.

Other Bill Terms

MIC Explained

Maximum Import Capacity (MIC) is the level of electrical capacity contracted between your business and NIE.

Where the Maximum Demand at any point of supply exceeds the agreed MIC. This breached MIC level becomes the Chargeable Service Capacity (CSC) for that current month and until reviewed by NIE on an annual basis.

Wattless charges

In large commercial or industrial premises, there are likely to be items of electrical equipment that require wattless energy to operate. Wattless energy is measured separately from your general units, and if you exceed a certain limit, it will give rise to a separate charge.

How to reduce wattless charges

You should contact your electrical contractor to fit power factor correction equipment. This will reduce the amount of reactive power you consume and help to avoid wattless charges on your bills.

Cost considerations

Weigh the cost of fitting special power factor correction equipment and how it will reduce wattless charges on your bill. The rate at which the new device will pay for itself naturally varies according to the level of wattless charges you have incurred, but generally speaking, if you have had a consistent wattless charge on every bill, the payback period is less than four years.

Fuel Mix disclosure

Here is the breakdown of the fuel sources we use to supply electricity and the associated environmental impact over the preceding year. Simply put, this tells you what the electricity you use is made from, and what emissions it creates.

Electric Ireland Disclosure Label

Applicable Period: January 2017 to December 2017



Electricity supplied
has been sourced from
the following fuel

Electricity Supplied
by Electric Ireland
(All Island)
(% of total)

Average All Island
Market for comparison
(% of total)

Coal 7.7% 9.8%
Gas 55.9% 40.0%
Renewables 31.9% 44.5%
Peat 3.8% 4.9%
Oil 0.5% 0.9%
Other 0.2% 0.0%
Total 100% 100%
Environmental impact
CO2 emissions 361g per kWh 325g per kWh



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