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Kilowatt hours (kWh) explained

The Kilowatt-hour (kWh) is a unit used by energy suppliers to work out how much you pay for gas and electricity. Here’s all you need to know about kWhs and saving money on your energy bill.

What is a kilowatt-hour?

A kilowatt-hour (kWh) is the standard unit of measurement used by energy suppliers for both electricity and gas. It’s the amount of energy you’d use if you kept a 1,000 watt appliance running for an hour.

For example, to use 1kWh of energy you’d need to use:

  • a 1,000 watt electric heater for one hour
  • a 100 watt light bulb switched on for 10 hours

The Commission for Regulation of Utilities (CRU) says the average dual fuel customer uses 4,200 kWhs of electricity and 11,000 kWhs of gas per year.

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What is a kilowatt?

A kilowatt (kW) is a measurement of power equal to 1,000 watts. A kilowatt describes how much energy an appliance is using, while a kilowatt-hour describes how much energy is used over a one hour period.

For example:

  • a 4,000 watt (4 kW) appliance would use 1kWh in 15 minutes
  • a 500 watt (0.5 kW) appliance would use 1KwH in 2 hours

How much does a kWh cost?

How much you pay per kWh will depend on the energy tariff you’re on and, if you have a day and night meter, what time of the day you use the energy.

The unit rate you see on your energy bills is the cost you pay per kWh. 1 kWh typically works out between €0.20 and 0.24 depending on the tariff you choose.

How many kWhs do appliances use?

Here’s the amount of energy used by some of the most common household appliances:

Appliance kWh Time  
Washing machine 1 kWh per cycle  
Dishwasher 1.25 kWh per cycle  
Tumble Dryer 2.5 kWh per hour  
Oven 2 kWh per hour  
Fridge-freezer 1 kWh per day  
Kettle 0.25 kWh per boil  
Plasma TV 1 kWh per 3 hours  
Laptop 0.5 kWh per day  

If you’d like to know about how to become more energy efficient around the home and cut the cost of your energy bill, visit our guide top energy saving tips.

How is KwH calculated for gas?

Your gas meter measures your gas usage in either cubic metres or cubic feet, depending on the meter.

To convert this measurement into kWh, energy suppliers use a ‘conversion factor’, which is published on your bill.

Can you use kWh to compare energy costs?

Yes, you can and you will get a much better idea of the savings you could make.

If you’re checking energy prices with a comparison site, you will get much more accurate results by entering your kWh use. You’ll find the figure on your bills or annual statement.

Make sure you enter the right time period. If you enter 2,500 kWh a month when you actually use 2,500 kWh a year, you might be surprised or misled by the prices you’re quoted.

How to cut energy costs and pay less

One of the easiest ways you can cut the cost of your energy bill is to use our free gas and electricity comparison service to compare unit rates and switch to a new deal. Here’s an example of the money you could save:

  • Electricity: The average user on a typical standard tariff can save up to €284 by switching to the cheapest electricity deal, and those with higher usage stand to save even more.
  • Gas: The average user on a standard tariff can save up to €138 if you’re an average user and even more if you live in a large household.

If you haven’t changed your tariff in over a year, compare electricity deals and make a switch to a discounted energy deal.

Switch and save up to €444 on your energy bills

It only takes a few minutes to find a cheaper deal and start saving