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Home & garden.

How we test electric heaters

We use climate-controlled rooms to test electric heaters. Find out more about how we separate the best electric heaters from the worst.
Jake Massey

No one tests electric heaters as thoroughly as Which?. We've tested widely available electric heaters from brands including Dyson, Ebac and Dimplex. You can use our test results to compare the heaters' performance on everything – from how fast they heat up, to how stable they keep a room's temperature. 

We test every electric heater in controlled conditions to ensure we make accurate comparisons between models. Only the very best can be recommended as Which? Best Buy electric heaters. 

Our independent electric fan heater reviews are designed to answer all your most important questions, including:

  • How well does the fan heater heat a room?
  • How stable is the temperature kept by the heater?
  • Does the fan heater deliver the power it claims on the box?
  • How much will the fan heater cost me to run?
  • How easy is it to use – and is it noisy?
  • If it's a smart heater, is it cybersecure?
  • Should I buy it? 

Want advice on the different types of electric heater, as well as guidance on how to buy the best? Check out our advice on the best electric heaters.

How well does the electric heater heat a room?

To help uncover which electric heaters are the best at heating a room, we've built two special test chambers: 

  1. One of them simulates a living room, measuring 3.5 x 4x 2.6m, and is extremely well insulated to stop heat loss through the walls.
  2. The second is a smaller refrigerated chamber, capable of being chilled to sub zero temperatures. Vents between the two chambers allow cold air to flow for our tests. 

We also compare the temperature 5, 10 and 15cm off the ground, just 50cm in front of the heater to make sure that the room is being heated uniformly.

Each electric heater starts the tests in a room temperature of 10°C. We switch the heater on and measure how long it takes for the room to reach a steady temperature, 10°C higher than at the start of the test. We then measure how hot the floor and air temperature is in front of the heater – this is to check it heats the room, not the floor.

How stable is the temperature kept by the electric heater?

To test how well the fan heater can keep the room temperature stable, we vary the temperature of the test chamber to stimulate mild, cold and very cold weather conditions. The best heaters will keep the room temperature stable, whether they have to work a little or a lot to do it. 

We also measure how much electricity it uses to reach the steady temperature so that you can make sure that your electricity isn't being wasted. 

Does the electric heater deliver the power it claims on the box?

We assess each heater to see whether it achieves the full power that's claimed by its manufacturer. We found that some heaters don't meet their manufacturer's claims – you can read our electric fan heater reviews to find out which models these are.

How easy is the heater to use – and is it noisy?

Three assessors examine how easy it is to set the heater up for the first time and how clear the instructions are. They also look at how easy it is to select different settings, including the ease of turning the electric heater on and off. Finally, they check to see whether it's easy to move the electric heater around when it is hot or cold.

We also rate how noisy the electric heater is and whether it falls over easily if you knock into it.

These tests simulate what you would experience if you bought the electric heater. Thanks to our test results, you can avoid any electric heaters that are tricky to set up and a pain to use. 

Is the electric heater cybersecure? 

So-called smart heaters, which can connect to your home network and be operated by your smartphone, tablet, computer or voice assistant, are becoming more common. To make sure that these internet-connected heaters aren't vulnerable to hackers, and that they're responsible with your data, we put them through our digital security tests.

We make sure that heaters are protected against common dangers such as:

  • vulnerabilities that let hackers and bots take control of your heater
  • poor security that could allow the information you transmit to the heater to be intercepted and read by non-intended recipients 
  • weak password standards and compatibility with insecure networks 
  • poor processing of your personal data, such as harvesting unnecessary data or making personal data hard to delete. We also find out where the servers that heaters send data to are located.

You might assume that your average hacker wouldn't give a fig about the data a smart heater holds. But the data they could gather from an insecure system could – for example – let them use your heater as an entry point to other parts of your home network and compromise other devices, or even learn about your routine (such as when you typically are and aren't at home). 

If we find any privacy and security issues, we notify the manufacturer and publish them in our reviews. These tests don't affect the score of a heater, but a heater that fails these tests won't be a Best Buy, and if it poses a serious risk to you, we'll name it a Don't Buy. 

Should I buy it?

All of these tests contribute to a portable fan heater's overall Which? test score. The overall score ignores the price of the freezer and is based on the following.

40% Heating (including speed and energy use)
30% Temperature stability
20% Operation (including noise and power)
10% Ease of use

A fan heater needs to score 72% or more in our tough tests to qualify as a Best Buy. Heaters that score 45% or less are highlighted as Don't Buy models to avoid.

Head over to our round-up of Don't Buy heaters to find the models to steer clear of.

Changes to our fan heater tests in 2020

We constantly improve our portable heater testing to ensure that we only recommend the very best models as Best Buys. This means that some models have been tested in slightly different ways. 

In October 2020, we changed our portable heater testing programme slightly. This included updating our thermostatic control test and changing how we evaluate heaters. This means that although you can generally compare results for portable heaters with those tested before 2020, the results don't directly correspond. However, each score still gives a very good indication of the overall performance of the portable heater.