How we test fridge freezers

We test more than 80 fridge freezers in our specialist lab each year. But how do we do it, and what makes Which? tests the most rigorous around?

Unlike free-to-access websites, which often get the fridge freezers they review free of charge from manufacturers, we pay for all the appliances we test. We spend around £80,000 every year buying fridge freezers for our tests, buying directly from major retailers, just like our members do.

We test fridge freezers in a laboratory, not a kitchen. Our percentage test scores are calculated purely on the measurements and ratings determined by a barrage of rigorous scientific tests. There's no room for personal bias. Read on to discover more about our intensive fridge freezer testing.

We go the extra mile to find the best fridge freezers

Chilling and freezing power: how quickly and how well does it chill and freeze 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 how well a fridge freezer will work in your kitchen and help keep your food fresher for longer.

To test chilling and freezing power, we set the room temperature to 23°C and part-fill the fridge freezer’s compartments with gel packs to simulate food already stored inside. Once these cool, 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 it takes for them to cool too.

What separates a good result from a poor one?

Brianna Watson, Which? fridge freezer expert, says:

'The best fridge freezers sail through these tests, chilling and freezing our test blocks in just five hours. The worst can take 48 hours – that’s two whole days.

'When food takes this long to chill or freeze, you not only lose nutrients, but you also compromise on safety, as warmer temperatures give microbes the chance to grow.'

Energy efficiency: how much energy does it use?

In view of the cost of living and climate crises, we updated our energy testing in 2023 to make it even more stringent. We use several tests to determine our new energy measurements, including how much energy each fridge freezer uses to:

• chill fresh food
• freeze fresh food
• keep food cool, measured over a 24-hour period – during this time, we open and close the fridge door several times to replicate how you'd use your fridge freezer in real life.

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 relative to the amount of usable storage space it offers – you can see the results on the technical specification tab for each fridge freezer review.

Because some of our older fridge freezer reviews still show the results of our previous energy-efficiency tests, models published before and after September 2023 aren't 100% comparable. However, the test scores for older models still give a good indication of how they'll work in your kitchen. 

What separates a good result from a poor one?

Your fridge freezer is on all day, every day, so you want one that’s energy efficient for its size. The difference is stark: the best models operate 39% below predicted energy levels, while the poorest burn through 170% more. An inefficient fridge freezer could waste hundreds of pounds over its lifetime.

Convenience: is it quiet and easy to use and clean?

A seemingly minor annoyance can quickly become a major drawback if you experience it on a daily basis. That’s why we assess things like how sturdy the shelves and drawers are, how smoothly the drawers slide in and out and whether you can fit a 2-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. This helps us to see how likely food and drink spills are to seep into hard-to-reach spots and crevices.

Finally, we assess the noise each fridge freezer makes in specially designed sound chambers within our lab. A fridge freezer can be quiet most of the time and then make irritating clunking sounds when the compressor switches on, so we assess sound quality over a prolonged period rather than taking a one-off decibel measurement.

What separates a good result from a poor one?

The best fridge freezers are easy to use and a dream to keep clean. The shelves slide out easily for rearranging and cleaning and have no pesky dirt traps where food crumbs can hide.

The worst we’ve tested have shelves that are tricky to remove and can harbour food spills and bacteria in those hard-to-reach places. Some of the bacteria that can be found in a dirty fridge include salmonella, pseudomonas, listeria and staphylococcus, which all cause illness.

The quietest fridges we’ve tested hum at a peaceful 20-30 decibels, about the same noise level as a whispered conversation. The noisiest rattle away at 50 decibels and make as much sound as an extractor fan. 

Manufacturer-recommended and optimum settings: do they cool the fridge to 4°C?

Your fridge freezer manual will tell you what setting to use, but sometimes these settings are far too warm or cold. And unless you check with a thermometer, you've no way of knowing whether your appliance is actually reaching the recommended temperature anyway. 

First, we test whether setting the fridge freezer to the manufacturer's recommended setting actually brings it down to an appropriate temperature of around 4°C in the fridge. 

We check this by following the manufacturer's instructions to set the thermostat, then record the temperature of gel packs in both the fridge and freezer compartments.

Next, we set the fridge freezer to the optimum or ideal setting: in other words, we make sure it's actually set to 4°C (some fridges fail the previous check).

If we can't set the fridge to exactly 4°C because of the dials or other available controls, we set it as near to this as we can, opting for slightly lower if needed rather than higher. Then we test its ability to cool and freeze food under those conditions. If there's a separate freezer thermostat, we set this to -18°C.

What separates a good result from a poor one?

The best fridge freezers have appropriate temperature recommendations and successfully achieve them.

The worst have recommended settings that make your appliance too warm, or the fridge too cold. This means that even if you follow the manufacturer's instructions and set your appliance to the recommended setting, you could end up storing your food at a different temperature from what you intended. Your food could go off more quickly and potentially become unsafe. 

Temperature stability: does it keep food chilled and frozen in the heat?

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 to prevent harmful bacteria from growing and to stop food from spoiling faster than necessary.

We raise the temperature in our test chamber to 35°C, replicating a heatwave, to see whether the gel packs inside remain safely chilled. 

What separates a good result from a poor one?

We’ve seen models that can reach internal temperatures of up to 12°C in the fridge section, which increases the risk of nasty bacteria growing. A good fridge freezer will maintain a stable temperature even in the hottest of rooms. 

Temperature stability: does it keep food frozen if the power goes out?

To see how a fridge freezer would cope in a power cut, we measure how long it takes for the temperature of our test loads in the frozen-food storage compartment to reach -9°C and -7°C, from a starting point of  -17°C, in a 23°C room. 

A fridge freezer with good insulation should be able to maintain a steady temperature, even without electricity. The door seal is particularly important; a poor seal will let warm air seep into the freezer and fridge.

What separates a good result from a poor one?

Good models are thoroughly insulated and can stay cold for a while after losing power. The best models take hours to warm up to -9°C and -7°C from a starting point of -17°C, so you shouldn’t worry too much if there’s a power cut. 

While it’s good to know a short loss of power won’t defrost your entire freezer, a power failure longer than an hour can still put your food's safety at risk (as microbes can grow in warmer temperatures, albeit slowly). So when in doubt, throw away the leftovers.  

Even models that cope well in this situation shouldn't be expected to do so for long, so don't ever be tempted to turn off your fridge freezer in the hope of saving money.

Veg compartment: does it keep salads crisp and fresh?

We test whether the drawer dries out your vegetables by measuring water loss. If the drawer has a slider to control humidity, we check its effectiveness. We also check the temperature of the drawer, which should be 0-4°C. 

If it goes above 4°C, the food inside will spoil more quickly, so we mark it down. 

If the temperature goes below 0°C – at which point your vegetables would turn icy and be ruined – we also mark it down. 

Because some vegetables prefer drier or more/less humid conditions than others, this test assesses suitability only for fruit and vegetables that like cold, humid conditions. Examples include asparagus, blueberries, broccoli, cabbage, carrots, celery, cherries, peas and strawberries.

What separates a good result from a poor one?

The best veg drawers cause very little (or no) water loss from fruits and veggies by properly controlling humidity and temperature. Some crisper drawers freeze delicate leafy greens and, unsurprisingly, don't score very well here.

Additional checks

We also make these checks when testing so we can include extra advice in our reviews. However, these results don't affect a product's overall test score.

Storage space: how much food does the appliance hold?

Don’t rely on claimed capacities to tell whether one fridge freezer is bigger than another, as manufacturers typically measure volume with all the shelves, drawers and door racks removed. This could make you think you have more storage space than you really do.

When we measure storage capacity, we leave everything in place and tell you how much space you can actually use to store groceries, measured in shopping bags. Check the technical specification tab of each fridge freezer review to compare realistic sizes.

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

Which? members can filter all our fridge freezer reviews by chilling power, freezing power, ease of cleaning and more of our expert test results

How we calculate the scores

Monika Gil, Which? senior scientific adviser, says:

'We regularly ask Which? members what matters most when choosing a fridge freezer. This insight helps me to update and fine-tune our rigorous test programme and to evaluate the data from our laboratory.

'Our 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.’

The Which? overall score is a percentage. This score reflects only our test results and ignores price completely. 

This means 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. 

The most important test results have a greater impact on a fridge freezer’s overall score:

• 35% chilling and freezing power
• 20% energy efficiency
• 10% convenience, including ease of use, ease of cleaning and noise
• 10% performance at the manufacturer’s recommended thermostat setting
• 10% performance at the optimum setting
• 5% keeping food chilled and frozen in a hot room
• 5% keeping food frozen in a power cut
• 5% how good the veg compartment is at keeping food fresh

How we choose the products

By testing new models almost every month, we give you our verdicts as quickly as possible. Each year, we test everything from dinky no-frills models for less than £300 to massive feature-packed American fridge freezers costing more than £1,000. This means we can showcase premium Best Buy models alongside Great Value fridge freezers that punch above their price.

Adishree Sharma, Which? senior market analyst, says:

'I actively track UK new launches, market trends, consumer search habits and sales data to ensure we test the fridge freezers people actually want to buy.

'To offer the best market coverage, I choose models from the most popular brands like Bosch, Hotpoint and Miele, ticking off all the ones you see at major retailers like AO, Currys or John Lewis. We don't just test the expensive new flagship fridge freezers that manufacturers are keen to sell you.'

Is it a Best Buy fridge freezer? What our verdicts mean

Our recommendations should help you to narrow down your shortlist, but it's always best to read our reviews in full to check for any dealbreakers before parting with your hard-earned cash.

Best Buy-recommended fridge freezers

These are the models that impress the most in our tests.

To become a Best Buy, a fridge freezer must score:

Best Buy fridge freezers typically do well in most, if not all, of our tests. This means they're likely to chill and freeze quickly and efficiently, have an accurate and reliable thermostat, maintain a safe and stable temperature whatever the temperature in your kitchen, and be easy to live with.

Eco Buy-recommended fridge freezers

If you want to make the most sustainable choice when buying a fridge freezer, an Eco Buy is for you. 

To become an Eco Buy, a fridge freezer must score:

It must also:

• get four stars or more for energy efficiency
• get four stars or more for chilling and freezing power
• achieve a good reliability record in our annual survey (discover which fridge freezer brand is the most reliable).

Eco Buy fridge freezers will have a lower impact on the environment over their lifetime compared with others we've tested.

We calculate this in two ways: how energy efficient the fridge freezer is, and how reliable – and therefore long-lasting – it's likely to be, so you don't have to repair or replace it as often.

Great Value-recommended fridge freezers

Great Value fridge freezers are at least 20% cheaper than the average price of the models we've tested (based on type).

To be deemed Great Value, a fridge freezer must score:

It must also:

• get three stars or more in our chilling and freezing tests
• get at least four stars for energy efficiency.

Don't Buy fridge freezers

Fridge freezers that are Don’t Buys should be avoided.

To become a Don't Buy, a fridge freezer must score:

Don’t Buy fridge freezers are beset with flaws, so don't expect them to take care of your food. We've also found some Don't Buys that are potentially unsafe. You should steer well clear.

Discover which models impressed in our lab in our fridge freezer reviews – use the Best Buy, Eco Buy and Great Value filters to help find the right model for you

Our cold-appliance experts

Running our test projects is a group effort, with several members from across the team contributing to each one.

We thoroughly re-evaluate our testing processes every year to ensure it's useful to you, and we ask the Which? community to tell us what matters the most when choosing a new fridge freezer. 

Here's the team that makes it happen:

Researcher & writer, Dr Brianna Watson: Brianna translates technical laboratory data into in-depth, unbiased product reviews and advice to separate the dream fridge freezers from the duds. She cuts through the marketing fluff and confusing jargon to ensure you invest in a model that actually delivers on its promises.

Home editor, Jackie Gallego: Jackie makes sure what you're reading is exactly what you want to know about fridge freezers. This means keeping a close eye on what's trending in the appliance world, seeking out key consumer questions we can help answer and finding new stories from our data to help empower our readers.

Senior scientific adviser, Monika Gil: Monika controls our test programme, meticulously converting hundreds of data points for each fridge freezer into easy-to-understand product scores and star ratings. Her rigorous analysis ensures that only the cream of the crop get our Best Buy or Eco Buy badges, while underachievers are marked as Don't Buys.

Senior market analyst, Adishree Sharma: Adishree keeps her finger on the pulse of what's happening in the world of cold appliances to curate our testing line-up, ensuring we only review what’s relevant to you. From fancy fridge freezers by major household names to rising stars, she looks beyond manufacturer spin to root out what you really want to buy.