We use cookies to allow us and selected partners to improve your experience and our advertising. By continuing to browse you consent to our use of cookies. You can understand more and change your cookies preferences here.

Home & garden.

Updated: 30 Jun 2021

Measuring your energy efficiency

Find out how to measure the electricity you're using, so you can work out how to cut down on your energy bill and be more efficient.
Which?Editorial team
Measuring energy_smart meter 475314

Once you know how much electricity you're using, you can work out how to save electricity and increase your energy efficiency. 

Do you know how much electricity you use at home every day? 

The cost of boiling a kettle, turning on the lights or charging your mobile phone all add up. With the price of electricity tariffs on the rise, there has never been a better incentive to start saving energy.

As well as saving you money by cutting your electricity bill, becoming more energy efficient will also mean less burning of fossil fuels. Burning fossil fuels to produce electricity increases carbon emissions, which are linked to climate change.

Smart meters make it quick and easy to know how much electricity you’re using. But whether or not you have one, read on to find out how much you use, and how to cut back.

The easiest way to save money on electricity is to make sure you're on the cheapest energy tariff. Use our independent switching service, Which? Switch, to look for a cheap electricity tariff.

Measuring your electricity use

How much electricity you use is usually measured in kilowatt hours, or kWh for short. An electrical item rated at 1,000W switched on for one hour uses 1kWh of energy (1,000W = 1kW).

  • A 20W CFL-type light bulb (equivalent to a 100W traditional bulb), on for one hour, uses 0.02 kWh of electricity
  • A 10W CFL-type light bulb (equivalent to a 60W traditional bulb), on for one hour, uses 0.01 kWh of electricity
  • A 50W laptop, on for one hour, uses 0.05kWh of electricity
  • A 600W microwave, on for 10 minutes, uses 0.1kWh of electricity

A good way to get a handle on how much electricity you're using is with a smart meter (and in-home display) or energy monitor. Using one of these to find out how much you’re using is the first step to working out how to cut back.

Smart meters and electricity use

Smart meters measure your energy use. They’re available for both electricity and gas and gradually being installed in homes.

You’ll be given an in-home display (IHD) when you get a smart meter installed. This connects with your smart meter via a wireless network and shows how much electricity (and gas) you’re using and how much it costs.

Boil your kettle and you’ll soon see on the IHD an increase in your electricity use. Some IHDs can also show you your electricity use over certain periods of time.

Some energy suppliers also provide mobile phone apps and information in your online account about your energy use.

Find out more in our smart meter guide.

Electricity costs on your bills

Electricity suppliers sometimes refer to each kWh of electricity as a 'unit of electricity' on your bill. They have a charge for each kWh (or each unit) - this is currently around 16-18p*.

So having a 20W CFL bulb on for one hour uses 0.02 kWh of electricity – 0.33p. With many household bulbs and electrical appliances being on for several hours a day, electricity costs can add up.

Most suppliers also have a daily standing charge for being connected to their electricity supply, before adding their charge per unit used. Some also charge a higher rate up to a certain amount of electricity used. Find out how much energy your home appliances use, and how it adds up, with our energy cost calculators.

*Based on the unit rate of Big Six standard variable tariffs, for customers paying by direct debit in June 2018.

Start saving electricity

There's lots you can do to start saving energy and money. For example, you can invest in more energy-efficient household appliances when it's time to replace them. 

When we test appliances in our lab, we measure how much electricity each one uses. This means you can use our reviews to pick the products that won't hike up your energy bill. 

Or, if you want to go straight to the heart of the problem, consider generating your own electricity using solar panels or switching to a cheap energy deal.

But it's not all about grand gestures. Smaller changes may shave only a few pence off your electricity bill. But in the long run, this can have a huge impact on the environment if we all get into the habit:

  • unplug your mobile phone's charger when the battery is fully charged
  • turn the light off when you leave the room
  • dry washing outside, rather than tumble-drying
  • only boil as much water as you need in the kettle

For more energy and money-saving tips, see 10 ways to save money on energy bills.