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
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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.
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:
As of 1 Nov 2024, a typical standard unit rate price (1 kWh) is 34.75 c/kWh for electricity and 11.645 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 to calculate appliance costs: Divide the wattage of your appliance by 1,000, multiply by the kWh unit price of your electricity tariff and then divide by 100. For example, on a tariff with a standard unit rate of 34.75c, an appliance with a wattage of 2250 (2.25 kWh) would use 0.78 cents per hour. Over an 8 hour period on full this would cost €6.26.
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.
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:
If you haven’t changed your tariff in over a year, compare electricity deals and make a switch to a discounted energy deal.
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