When you look at your electricity bill or app, you’ll see the amount of electricity you’ve used is measured in kilowatt hours (kWh). Let’s explore what a kWh is so you’ve got a better understanding of how your energy usage is measured and priced.
What is a kWh?
A kilowatt hour (kWh) is a unit for measuring how much electricity is used over a period of time. Energy suppliers, like ourselves, use it as a way to track how much energy is consumed by households. One kilowatt hour is the amount of energy you need to run a 1,000-watt (1kW) appliance for one hour.
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What can 1 kWh power?
One kWh can power different appliances for different lengths of time, depending on how much electricity they need to run. For example, 1kWh can power your:- Microwave oven (800 watts) for 1 hour 15 minutes
- Electric oven (2kW) for 30 minutes
- Kettle (3kW) for 20 minutes
- Air fryer (1.5kW) for 45 minutes
- Vacuum cleaner (1.4kW) for 43 minutes
- Tumble dryer (3kW) for 20 minutes
- Washing machine (850 watts) for 1 hour 10 minutes
- TV (80 watts) for 12 hours 30 minutes
- Electric heater (1.5kW) for 40 minutes
- Electric fan (100 watts) for 10 hours
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How to calculate kWh?
Working out the kWh of your appliances is a good way to determine which appliances are using the most electricity. To calculate kWh, multiply the power consumption of your appliance (in kW) by the time it's used in hours.
Here's how:- Check your appliance's label or manual for a power rating, either in watts (W) or kilowatts (kW). If it's in watts, divide by 1000 to give kW.
- Work out how long the appliance is used in hours. If the time is in minutes, divide by 60 to give hours.
- Then use this formula: kWh = appliance power (kW) × time used (hours)
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What is the difference between a kW and a kWh?
A kilowatt (kW) measures power (how much electricity an appliance needs to run), whereas a kilowatt hour (kWh) measures energy (the total amount of electricity the appliance uses over time).
A simple way to picture it is to think about a car: kW is like the speed of the car, whereas kWh is like the distance travelled. The faster the car goes or the longer it drives, the more distance it covers.
Electricity works the same way, higher power or more time means more kWh used.
How much does a kWh cost?
The cost of a kilowatt hour depends on your electricity supplier and the tariff you’re on. Every tariff has a unit rate, which is the price you pay for each kWh of electricity you use. Some tariffs charge a single rate at all times, while others offer different prices depending on whether you use electricity during the day, evening or night.
You can find your exact unit rate by checking your electricity bill or looking up your tariff’s rates online.
As an example, if your unit rate was 30p per kWh here’s how the costs could add up:
- Running a 1 kWh appliance for one hour would cost 30p.
- If your home uses 8 kWh in a day, that would cost £2.40.
- If you use 250 kWh in a month, your electricity would cost £7
Check how much you pay per kWh
If you’re a Power NI customer, check our unit rates to see how much you pay per kWh. And even if you’re not with us, see how our rates compare to your current electricity supplier!
Compare Power NI unit rates
Average kWh Usage in Northern Ireland
Understanding how much electricity a typical home in Northern Ireland uses can help you compare your own usage and spot opportunities to save. Below, you’ll find the latest average figures for households, along with examples of how much electricity common appliances and electric vehicles use.
What is the average kWh usage in households in Northern Ireland?
The latest UK government figures show that the average home in Northern Ireland uses around 3,179 kWh of electricity per year. This works out to roughly 265 kWh per month, 61 kWh per week, and around 8–9 kWh per day.
| Average kWh Usage in Households | |
| Per Day | 8-9 kWh |
| Per Week | 61 kWh |
| Per Month | 265 kWh |
| Per Year | 3,179 kWh |
How many kWh do household appliances use?
Different appliances use different amounts of electricity depending on their wattage and how long they’re used. We have a complete guide on which household appliances use the most electricity, but here’s a quick overview of typical daily usage for common household appliances.
| Time Used (Daily Average) | Approx. kWh Usage | |
| Microwave oven | 5 mins | 0.66 kWh |
| Electric oven | 45 mins | 1.5 kWh |
| Kettle | full boiled, 5 times | 0.75 kWh |
| Air Fryer | 30 mins | 0.75 kWh |
| Vacuum Cleaner | 10 mins | 0.23 kWh |
| Tumble Dryer | 40 mins | 2 kWh |
| Washing Machine | 40 mins | 0.5 kWh |
| TV | 3 hours | 0.24 kWh |
| Electric Heater | 2 hours | 3 kWh |
| Electric Fan | 2 hours | 0.2 kWh |
How many kWh do electric vehicles use?
According to EV Database, electric vehicles typically achieve around 3 to 4 miles per kWh in everyday driving. This means the car uses roughly 0.25–0.33 kWh of electricity per mile, depending on the model and driving conditions. If we round this to 0.3 kWh of electricity used per mile, here are examples of EV energy used to complete typical journeys across Northern Ireland.
| Commute Type | Distance Driven (Daily Average) | Approx. kWh Used |
| Short School Runs / Errands | 10 miles | 3 kWh |
| Light Daily Driving | 12 miles | 3.6 kWh |
| Lisburn ↔ Belfast | 18 miles | 5.4 kWh |
| Newtownabbey ↔ Belfast | 22 miles | 6.6 kWh |
| Bangor ↔ Belfast | 28 miles | 8.4 kWh |
| Derry/Londonderry ↔ Coleraine | 34 miles | 10.2 kWh |
| Antrim ↔ Belfast | 40 miles | 12 kWh |
| Portadown ↔ Belfast | 52 miles | 15.6 kWh |
| Ballymena ↔ Belfast | 56 miles | 16.8 kWh |
*Estimates based on ~0.3 kWh per mile. Actual usage varies by ev model, speed, temperature and other factors.
Maximise Your Miles per kWh with EV Home Charging
Our home EV chargers and EV tariffs make it easier and more efficient to charge your electric vehicle at home. Find the perfect combination to suit your lifestyle and driving habits.
Explore EV Home Charging Options
How to save kWh of electricity
If you’ve made it this far, you’ll know that reducing the number of kWh you use is one of the easiest ways to lower your electricity bill. If you’d like detailed advice on how to reduce electricity usage, you can visit our full guide on saving electricity at home - but to finish off, here are a few quick ideas to get you started…
Run appliances more efficiently
Use full loads, shorter cycles and eco settings where possible.
Choose a tariff that suits your usage
Plans with lower unit rates (or cheaper off-peak hours) reduce the cost of every kWh you use.
Avoid leaving appliances on standby
Turn devices off at the plug when not in use, instead of leaving them on standby.
Switch to LED lighting
LED bulbs use far fewer kWh than older halogen or incandescent bulbs.
Use the right appliance for the job
For smaller meals, microwaves and air fryers use fewer kWh than ovens.
Cut down on hot water electricity
Shorter showers and less reliance on electric showers can make a noticeable difference.
Frequently asked questions
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What is considered good miles per kWh for electric vehicles?
Electric vehicles typically achieve 3 to 4 miles per kWh in everyday driving. Anything around 4 miles per kWh or more is considered very efficient. Your exact figure will vary depending on the model of the car, how fast you drive, road conditions and the weather, as EVs tend to use more electricity in colder temperatures.
The amount of electricity your EV actually draws will depend on your car’s battery and how full it is, but the charger’s kW rating tells you the maximum amount it can deliver each hour. -
What is a good kWh per day for solar panels?
A good daily output for a typical 4kW solar system in the UK or Northern Ireland is around 8-12kWh per day in the summer, and around 2-5kWh per day in winter. However, the daily energy output from solar panels will vary based on factors like the roof direction, weather conditions, and size of the solar system. -
Are there other ways to measure kWh usage at home?
Yes. Alongside using the kWh formula, there are a few practical ways to measure how much electricity your appliances and household are using:- Use an energy monitor
- Check your meter, bill or app
- Use smart plugs or appliance monitors
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How can you work out gas kWh?
Gas usage is usually recorded on gas meters in cubic metres. To convert cubic metres into kWh you have to multiply the units on your gas meter by something called the conversion factor. This is the amount of energy in kWh released by burning 1m3 of gas. It changes based on the calorific value of the gas, which in turn varies based on where it’s sourced, its physical composition and local temperatures.
To convert a gas meter reading into kWh, multiply your meter reading by the volume correction factor (1.02264), multiply by the calorific value and divide by the conversion factor. -
What are some other measures of electricity?
We’ve discussed that watts and kilowatts measure power and the kWh measure energy. For industrial scale measuring, electricity is also measured in megawatt hours (MWh) and gigawatt hours (GWh). One megawatt (MW) is 1,000kW and one gigawatt is 1,000MW. -
What kWh is a home EV charger?
Most home EV chargers are rated at 7 kW, which means they can use up to 7 kWh of electricity for every hour of charging. Slower 3kW chargers use around 3 kWh per hour, while faster 22 kW chargers are usually only available with three-phase power.
