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Home & garden.

Updated: 14 Mar 2022

How we test microwaves

Microwaves need to impress in our tests by heating and defrosting food evenly and being simple to use, so you get a succulent, evenly-cooked meal fast.
Rebecca Jakeman

What makes a Best Buy microwave?

We will only recommend microwaves that heat and defrost your food quickly and evenly, leaving no overdone or cool parts. If the microwave oven also has a grill or conventional oven, we'll test these functions, too. Watch the video above to see why a Best Buy microwave oven will make a real, practical difference to you.

All microwaves go through a set of rigorous tests to assess how good they are at key jobs you'd expect them to do. Our reviews answer the following important questions: 

  • Is the microwave good at cooking food?
  • How good is it at defrosting?
  • How good is it at steaming?
  • If it's a combi microwave or has a grill, are these features any good?
  • Is it noisy?
  • Is it easy to use?
  • Should I buy it?

Head to our microwave reviews to discover which ones come out top of our testing and will guarantee great results. 

Alternatively, read on to find out more about exactly how we test microwave ovens.

Is the microwave good at heating food?

We test how well each microwave cooks or reheats food by using a special substance which has a similar consistency to a lasagne when heated in a microwave. We heat the test food on full power and record how evenly a microwave heats it up, including whether all parts of the food reach a safe temperature and whether the microwave dries food out. 

We also check how well microwaves maintain their heating power if used to reheat several meals in a row. Many microwaves lose power with repeated use, which means that you'll end up needing to cook your food for longer.

The best microwaves heat food quickly and evenly without drying it out. The worst take far too long to heat food up, don’t get food hot enough or leave it dry and unappetising.

How good is it at defrosting?

We use slabs of lean, minced beef which have been frozen for 12 hours, and set the microwave to defrost according to the manufacturer's instructions. We record the difference between the highest and lowest temperatures and check for hot or cold spots in the meat. We also defrost frozen mince using pre-set auto-defrost programs where available. 

The best microwaves defrost meat evenly, the worst start cooking some parts while leaving other parts still frozen - we've seen some which have a difference of more than 20 degrees, while the best will leave a perfectly defrosted slab which is an even temperature throughout.

How good is it at steaming?

In 2018, we updated our microwave tests based on feedback from Which? members to include a test of how well microwaves can steam food. 

Some have a dedicated steam setting, and if there is one we use it, but you don't need a special program to steam successfully in your microwave. You can simply pop veg into a bowl with a few tablespoons of water and a loosely covered lid.

We assess how well each microwave can steam a complete meal consisting of salmon, potatoes and broccoli. We check if any of the food is uncooked after steaming, using temperature probes in different parts of the fish, veg and potatoes.

We've found that some microwaves are able to produce a lovely evenly steam-cooked meal while others over-cook some parts and leave others near-raw.

Are the grill and convection cooking functions any good (if applicable)?

For combination microwaves and microwaves with a grill, we test these functions to see if they work well.

To check how effective the grill is, we cover the grill rack with white, crustless bread and measure the spread and evenness of heating. The best grill microwaves will evenly toast more than 90% of the bread. The worst hardly brown any of the bread at all.

We test the convection function on combination microwave ovens works by baking trays of fairy cakes. The best combination microwaves will produce well risen, evenly browned cakes. Poor models will burn the cakes, or leave some of them uncooked.

Is the microwave noisy?

We record microwave noise when heating on full power and when defrosting. The quietest microwaves make about 47dB of noise in microwave mode, while the noisiest make 62dB. This will sound three times louder – and is loud enough to irritate some people.

Is it easy to use?

We assess how easy it is to set microwaves and to carry out simple tasks such as opening the door and cleaning them. The best microwave ovens are very easy to use and are intuitive to set. For the worst microwaves you’ll need to keep the instruction manual to hand.

If you have difficulty with strength or dexterity in your hands, take a look at our selection of the best microwaves, which includes advice on that to look out for.

Should I buy it?

The tests above contribute to an overall test rating for each microwave oven, which we convert to a percentage score.

We know that certain functions of microwaves are more important than others, so we weigh our testing to reflect this. You've told us that how well a microwave oven heats food is the most important aspect, so this test accounts for a minimum of 40% of the overall score. 


  • 40% microwave heating
  • 25% defrosting
  • 25% ease of use
  • 10% steaming


  • 35% microwave heating
  • 25% defrosting
  • 25% ease of use
  • 7.5% grill 
  • 7.5% steaming


  • 35% microwave heating
  • 25% defrosting
  • 25% ease of use
  • 5% convection
  • 5% grill 
  • 5% steaming

All microwaves need to score 74% or more for us to recommend them as a Best Buy. We think that any microwaves that score 45% or less should be avoided, so we highlight them as a Don't Buys.

Changes to our testing:

In 2018, we updated our tests to make them even more challenging, including adding a new test on steaming food, based on member feedback about how you use your microwave. This means that scores from microwaves tested in February 2018 or later aren't directly comparable with the scores of microwaves tested before this date.