Freezers: How we test freezers

Which? freezer tests

A great freezer will keep food safely frozen when your kitchen heats up or cools down. It will run quietly, be powerful enough to freeze a large load of fresh food in one go and offer plenty of useable storage space. And it won't add a fortune to your energy bills. 

To find the models that fit this bill, we carry out up to 215 checks, measurements and tests on each freezer at our temperature-controlled labs. 

To read reviews of all the freezers we've tested, head straight to our freezer reviews.

Freezer power

If you like to bulk-buy and freeze fresh produce or cook large batches of homemade meals to pop in the freezer, you’ll need a freezer that can handle a large amount of fresh food. We measure how many kilograms of fresh, room-temperature gel packs each part-filled freezer can freeze to -18°C in 24 hours.

We also test how well insulated the freezer is to see how long it will keep food safely frozen in a power cut. To do this we load both compartments with gel packs, allow the appliance and packs to acclimatise, then switch the power off. We time how long it takes the packs’ temperature to rise from -18°C to -9°C, which is the point at which you would have to discard the contents of your freezer. A good freezer will keep food frozen for at least 24 hours.

Freezer storage space

The more storage space inside your freezer, the more groceries you can pack away and the less frequently you’ll need to shop. Yet two appliances of the same size might have more than 20% difference in usable space due to differences in design.

We measure storage space with all of the storage features in place and don’t count any wasted areas. Our sizes give a more realistic indication of the amount of space you can actually use for storing groceries, compared with manufacturers’ claimed capacities - these are usually measured with all of the shelves, trays and drawers removed.

Freezer energy costs

Running a freezer over its lifetime can be expensive – because it’s always switched on you will constantly pay to power it. We measure how much energy each freezer uses over 24 hours in a 25°C room, then calculate what this will add to your yearly energy bill.

To compare the true lifetime costs of freezers, combining the purchase price and running costs over several years, check out our energy costs calculator tool.

We also rate each freezer on energy efficiency - based on the amount of energy each appliance uses to freeze the usable storage space available. This shows you whether each model is energy efficient for the space you’re paying to power. 

For products that successfully marry Best Buy performance with superb energy efficiency in our in-depth tests, we’ve introduced our Which? Energy Saver logo - you can find out more about how this is awarded in our guide to freezer energy costs.

Ease of use and cleaning

Some freezers are easier to set up and use than others. We rate the type of display, position of the thermostat control and how easy it is to adjust, and whether it comes with a high-temperature or door-open alarm. To find out more about the the various features you may find on a freezer read our features explained guide.

We also rate how sturdy the drawers or trays are, how easy they are to open, how easy the appliance is to clean, the quality of the storage features and whether it's frost-free. In total, our expert testers carry out up to 86 ease-of-use tests on each freezer. 

And, because it's virtually impossible to spot how noisy a freezer will be while you're in the shop, our independent testers rate not only how loud each freezer is when it's cooling, but also how annoying the pitch and tone are.

Thermostat settings and temperature stability

Most instruction manuals come with a setting or guide for positioning the thermostat - but following these doesn't always lead to ideal temperatures for keeping food safely frozen.

When we set a freezer up in our test lab we follow the recommended setting, allow it to acclimatise and record the temperature of gel packs inside. This tells us how cold food would actually be if you plugged the freezer in 'straight from the box' without checking the temperature with a fridge/freezer thermometer.

The best appliances will chill the packs to -18°C or lower - first time. The worst will run too warm or cold, and need lots of thermostat-tweaking to get the running temperature right.

We also test temperature stability - because room temperatures can vary widely over the course of a day and at different times of the year. To do this we raise the temperature in our test chamber to 32°C, then we lower it to a chilly 10°C. We measure how stable the internal temperature remains - good freezers shouldn’t get warmer than -18°C.

Freezer scores explained

Freezer total test scores ignore price and are based on:

• Accuracy of recommended thermostat setting 10%
• Temperature stability 20%
• Freezing power 20%
• Insulation 15%
• Convenience 10%
• Noise and vibration 10%
• Energy use 15%

Fridge freezer testing changes for 2012 

At the beginning of 2012 we raised the typical 'room' temperature in our test chamber from 20°C to 25°C to see how well each freezer keeps food frozen when it's forced to use more energy, just as it is in your kitchen when the door's opened and closed and the temperature fluctuates. 

Energy costs are rising and freezers are becoming more efficient, so we've changed the way we rate energy use - we’ve increased the amount energy use contributes to the final score, and made it harder for freezers to score three, four or five stars.

For freezers tested before 2012, the score was based on the same total test score as above, but insulation and energy use contributed 20% and 15% respectively. For chest freezers, freezing power and energy use contributed 25% and 10% respectively.

Though you can generally compare results for freezers tested before 2012 with those tested after (this is noted under the specifications tab in each review), the results don’t directly correspond. However, each score still gives a very good indication of the overall performance of the freezer.

More on this...

• See which models make the grade as Best Buys in our freezers review area
• Find our which freezer brands last in our reliability survey
• To find the best model for your needs compare freezer features and prices