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How we test fridge freezers

By Ben Slater

What makes a fridge freezer great? See how our tests reveal the fridge freezers that help ensure your food is at its freshest when you eat it.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

We test more than 125 fridge freezers in our specialist lab each year, but what do we actually do to them and why are our tests the most rigorous around?

Jump straight to:

Why our fridge freezer tests are different

Unlike free-to-access websites, which typically get the fridge freezers they review free of charge directly from manufacturers or their PR representatives, we buy all the appliances we test ourselves so you can have complete trust in our verdict.

As well as using multiple testers in a lab-based scenario, the Which? overall percentage score is calculated purely on the measurements and ratings supplied by the lab, meaning there's no room for unconscious bias when giving an overall rating. 

What are Which? Best Buys and Don’t Buys?

The fridge freezers that impress the most in our tests are made Best Buys. As of November 2019, a fridge freezer that scores at least 74% earns our Best Buy recommendation, but you should still read our reviews to check for any factors that might impact your buying decision.

Fridge freezers that score 45% or less, on the other hand, are Don’t Buys and should be avoided at all costs.

  • Best Buy fridge freezers typically do well in most, if not all, of our tough tests, so they're likely to chill and freeze quickly and efficiently, have an accurate and reliable thermostat, maintains a safe and stable temperature whatever the temperature in your kitchen and also be easy to live with.
  • Don’t Buy fridge freezers are beset with flaws, so don't expect them to provide a good home for your food.  We've also found some Don't Buys to be potentially unsafe. You should steer well clear.

How is the Which? score calculated?

The Which? overall score is a percentage. This score only takes into account the results of our tests and ignores price completely. 

This means that all fridge freezers are tested on exactly the same scale, so you can compare any model at any price and know how it measures up against its rivals in key areas. All fridge freezers are tested in the same way, regardless of the manufacturers’ claims. 

Weightings and star ratings 

A Which? test score is made up of dozens of individual tests and checks, from key factors such as chilling and freezing speed to energy efficiency, quietness and ease of use.

To keep things simple, the most important scores are shown as star ratings out of five on each fridge freezer’s Test Results page as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether a model is right for you.

The most important test results have a greater impact a fridge freezer’s overall score, as the graphic below shows.

Our testing criteria

Below are the key testing categories and how we evaluate each one:

Chilling and freezing power 

Key question: How quickly will the fridge freezer chill and freeze my food?

The faster your groceries cool, the longer they’ll last, the more nutrients they’ll retain and the fresher frozen food will be when you defrost it.

Our tough tests are designed to reveal what a fridge freezer will be like in your kitchen. That way, you know that the best fridge freezers will create the best storage conditions for your fresh and frozen food and help keep your food fresher for longer.

To do this, we set the room temperature to 25°C and part-fill the compartments with gel packs to simulate food already stored inside. Once these have cooled, we add more gel packs – roughly equivalent in size to what you’d buy during a top-up shop for fresh food – and record the time taken for these packs to cool.

The best fridge freezers chill and freeze in a matter of hours, whereas the worst struggle to complete our tests during two whole days of testing.

Chilling power makes up 25% of the total fridge freezer score, while freezing power accounts for 15%.

Fridge freezer energy use 

Key question: How much will the fridge freezer add to my energy bills?

It’s impossible to reduce a fridge freezer’s running costs, as you can’t switch it off to save electricity. So it’s a good idea to buy a fridge freezer that’s energy efficient for its size.   

We measure how much energy each fridge freezer uses to keep cool over 24 hours, as well as how much it uses to chill and freeze fresh food. We then calculate what this is likely to add to your energy bill. To see whether a fridge freezer is cheap to run for its size, we also rate its energy use against the amount of useable storage space it offers – you can see the results on the technical specification tab for each fridge freezer review.

Energy use accounts for 15% of the overall fridge freezer score.

Temperature stability 

Key question: Will the fridge freezer keep my food safely chilled and frozen?

It’s crucial that a fridge freezer keeps your food safely chilled and frozen around the clock, even when your kitchen heats up and cools down. This is because an evenly cool environment is essential for preventing harmful bacteria from growing and stopping food from spoiling faster than necessary.

So we raise the temperature in our test chamber to 32°C and see whether the gel packs inside remain safely chilled. We then lower the room temperature to a chilly 10°C and recheck the temperature of the gel packs.

Temperature stability in warm and cold rooms makes up for 10% of the score for a fridge freezer.

Fridge freezer storage space 

Key question: How much food will I be able to store in the fridge freezer?

Don’t rely on claimed capacities to tell whether one fridge freezer is bigger than another, as manufacturers typically measure volume with all of the shelves, drawers and door racks taken out, which makes you think you have more storage space than you actually get.

When we measure storage capacity we leave everything in place and tell you the amount of space you can actually use for storing groceries. Check the technical specification tab of each fridge freezer review to compare realistic sizes.

Fridge freezer capacity doesn’t contribute to our fridge freezer test scores, because it would favour very large American-style fridge freezers, which isn’t what everyone is looking for.

Some fridge freezers have a lot less storage space for your groceries than others - even those that appear to be the same size.

Thermostat reliability 

Key question: Can you trust the fridge freezer thermostat?

Unless you check with a thermometer, it’s impossible to know whether or not your fridge freezer has chilled and frozen to the right temperatures when you first set it up in your kitchen. So we test how accurate the recommended thermostat settings are by following the instructions and recording the temperature of gel packs in both the fridge and the freezer compartments.

The best fridge freezers get the temperature spot on, but the worst are way off - meaning your food would be stored at potentially unsafe temperatures and go off more quickly than it should.

The accuracy of recommended thermostat setting accounts for 10% of the total test score.

Ease of use and cleaning 

Key question: How easy is the fridge freezer to use and clean?

Some fridge freezer are easier to use than others, and a seemingly minor flaw will soon become a major drawback after you’ve experienced it on a daily basis. So we rate ease of use, looking at aspects such as how sturdy the shelves and drawers are, how smoothly the drawers slide in and out, and whether you can fit a two-litre bottle of water in the door rack.

We also spray cherry juice inside each fridge, let it dry to a sticky mess and then rate how easy it is to clean, to see how likely food and drink spills are to seep into hard-to-reach spots and crevices.  The best fridges are easy to keep clean. The worst have dirt traps that can harbour food spills and nasty bacteria.

Ease of use and cleaning account for 15% of the total test score.

The best fridge freezers are easy to clean and don't have dirt traps that can harbour food spills and nasty bacteria.

Noise testing 

Key question: How noisy will the fridge freezer be in my kitchen?

Every fridge freezer we test is assessed for noise in specially designed sound chambers within our lab. Because it's possible for a fridge freezer to be quiet most of the time and then make irritating clunking sounds when the compressor switches on, we assess sound quality over a prolonged period of time, rather than just taking a one-off decibel measurement.

The quietness of a fridge freezer contributes 5% to the total test score.

Pick the perfect fridge freezer with Which? reviews

At Which?, we continually monitor and vary the assessments that underpin our reviews to take account of changing standards and areas of concern.

All fridge freezers need insulation to keep cool. This insulation is flammable, so it's essential that it's sufficiently protected in the unlikely event of a fire. The backing that covers this insulation is currently made from either plastic, metal or aluminium laminate.

Our tests have revealed that plastic backing can be highly flammable. We're not recommending any refrigeration appliances with flammable plastic backing. All fridge freezers with this type of backing have been made Which? Don't Buys, regardless of how else they have performed in our chilling and freezing tests.

Find out more about fridge freezer safety.

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