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?

All your household appliances and gadgets consume electricity measured in kilowatts.

A kilowatt describes how much energy an appliance uses and is a power measurement equal to 1,000 watts. The reason that kilowatts are used instead of watts is due to the volume of electricity used by most appliances.

Example conversion:

  • 4,000 watts = 4 kW
  • 500 watts = 0.5 kW
  • 10 watts = 0.01 kW

Switch and save up to €779 on your energy bills

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

What is a kilowatt-hour?

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

Some appliances are more energy-hungry than others. Here are some estimates of which household appliances could use 1 kWh:

Appliance Watts Time period  
Electric shower 10,000 watts 6 minutes  
Immersion heater 3,000 watts 20 minutes  
Oven 2,000 watts 30 minutes  
Electric heater 1,000 watts 60 minutes  
Light bulb 100 watts 10 hours  
42” LED TV 80 watts 12 and a half hours  
Electric blanket 150 watts overnight  
Wireless router 8 watts five days  

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

kwh energy bill lady

How much does a kWh cost?

The unit rate you see on your energy bills is the cost you pay per kWh. How much you pay per kWh will depend on:

  • your energy supplier
  • your energy tariff
  • discounts applied
  • time of use*

As of 1 March 2024, a typical standard unit rate price (1 kWh) is 35.83 c/kWh for electricity and 12.005 c/kWh for gas (inc VAT).

* If you’re on a smart plan or have a day and night meter

How many kWhs do appliances use?

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

Appliance kWh Time  
Washing machine 1 kWh per cycle  
Dishwasher 1.25 kWh per cycle  
Tumble Dryer 2.5 kWh per hour  
Cooker hob 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 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 usage in either cubic metres or cubic feet, depending on the meter. To convert this measurement into kWh, energy suppliers use a ‘conversion factor’. The conversion factor is a measurement of the heat content of the volume of gas measured.

How are kWh used to calculate electricity?

Your bill is calculated by monitoring the amount of kwH used. Your electricity usage is measured by the difference between your current and previous meter readings. Your supplier will multiply this difference by your unit rate to calculate your bill.

Can you use kWh to compare energy costs?

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

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

Compare energy prices now

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 €505 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 €292 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 €779 on your energy bills

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