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 how long it would take some common household items to 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 |
How much does a kWh cost?
The cost of a kilowatt-hour (kWh) varies depending on
As of August 2025 in Ireland, typical electricity unit rates range roughly from 25 to 35 cents per kWh (including VAT), but your exact price might be higher or lower depending on discounts, standing charges, and whether you have a smart meter.
For gas, the unit cost is usually lower, often around 11 to 13 cents per kWh (including VAT).
Remember, the unit rate is just one part of your energy bill. Standing charges, taxes, and other fees also affect your total cost.
To find out exactly how much you pay per kWh, check your latest energy bill or contact your supplier.
You can also use our energy comparison tool and enter your typical kWh usage to help you discover cheaper tariffs and save money.
* If on a smart plan or have a day and night meter
How much energy do your appliances use?
Here’s the amount of kWhs 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 | |
| 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 34.03c, an appliance with a wattage of 2250 (2.25 kWh) would use 0.765 cents per hour. Over an 8 hour period on full this would cost €6.12.
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.
What does the average Irish household use?
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.
These figures are based on national averages and can vary depending on factors such as:
- Household size
- Home size and type
- Energy efficiency
- Heating methods
- Usage habits
Can you use kWh to compare suppliers?
Yes, you can, and it’s one of the best ways to compare energy costs between suppliers and tariffs.
By knowing how many kWh you consume, you can compare the unit rates (price per kWh) that different suppliers charge. This helps you understand which tariff offers the best value for your actual energy use.
When using a comparison website like Switcher.ie, entering your annual or monthly kWh usage gives you personalised price estimates, making it easier to find cheaper deals tailored to your consumption. You can find the figure on your bills, app or online account.
Keep in mind that other factors like standing charges, discounts, and time-of-use rates can also affect your total bill, so consider these alongside the kWh rates when comparing plans.
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.
Switch and save up to €776 on your energy bills
It only takes a few minutes to find a cheaper deal and start saving
