How we test freezers
By Jess O'Leary
Our tests reveal the freezers that freeze fast, to keep your food as fresh and nutrient-packed as possible. Find out more about our tests.
Which? Best Buys exist to showcase the very best products you can buy. Our video, above, reveals what you can expect from a Best Buy freezer - and how the terrible freezers are a poor substitute.
We’ve tested the latest models to help you find the best possible freezer for your food. Head to our freezer reviews to find out:
- How well will the freezer freeze my food?
- Will the freezer keep my food safely frozen?
- Is the freezer cheap to run for its size?
- Can I trust the freezer’s thermostat?
- Should I buy it?
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How well will the freezer freeze my food?
The faster food freezes, the fresher and more nutrient-loaded it will be when you defrost it. Plus there’s less chance for harmful bacteria to thrive. Fast cooling is essential if you like to bulk-buy and freeze large amounts of fresh food, or cook large batches of homemade meals to pop in your freezer.
Some freezers are super-fast, but some can take days to cool your food to safe temperatures. To test this, we load each freezer up with food equivalent gel packs - to simulate food that’s already stored inside – and allow them to acclimatize. We then test how quickly the freezer can freeze a fresh load of room-temperature gel packs. We also test whether the items already stored inside warm up during the process.
To see which models ace our freezing tests, check out our Best Buy freezers.
Will the freezer keep my food safely frozen?
Room temperatures can vary widely over the course of a day and at different times of the year. So to make sure your freezer is keeping your food frozen around the clock, we raise the temperature in our test chamber to 32°C, and then we lower it to a chilly 10°C.
The best freezers keep food safely frozen 24/7 – whatever the temperature is outside. But some struggle to maintain an even temperature, causing food to partially thaw and re-freeze as the temperature outside fluctuates.
Is the freezer cheap to run for its size?
Running a freezer over its lifetime can be expensive – because it’s always switched on, you will constantly pay to power it. So we measure how much energy each freezer uses over 24 hours in a 25°C room and how much it uses to freeze fresh food. We then calculate what this will add to your yearly energy bill.
We also rate how energy efficient each freezer is – based on the amount of energy each appliance uses for the usable storage space available. This shows you whether a freezer is energy efficient for the space you’re paying to power.
Can I trust the freezer’s thermostat?
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 placed 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 freeze to perfect temperatures, first time. The worst will be way off - it will run too warm or cold, and need lots of thermostat-tweaking to get the running temperature right.
A good thermostat creates the perfect temperature for storing frozen food. A bad one is way off.
How long will a freezer keep my food safely frozen in a power cut?
A decent freezer will keep food frozen for at least 24 hours with no power. To test how well insulated a freezer is, we load the appliance with gel packs, allow them to acclimatise, and then switch the power off. We time how long it takes the packs’ temperature to rise by 9°C.
We find that the temperature inside the worst models soon rises, meaning if you experience a power cut, the food in your freezer is likely to thaw more quickly than it should.
Is a freezer quiet, easy to use and easy to clean?
Some freezers are easier to set up and use than others. So we rate aspects such as how sturdy the drawers are, how smoothly the drawers slide in and out, and whether the drawers slide out far enough for you to be able to fit items inside.
We also rate how easy the thermostat is to adjust, how simple any functions are to programme and how easy it is to clean.
And, because it's impossible to spot how noisy a freezer will be while you're in the shop, we rate how loud each freezer is when the compressor kicks in, helping you avoid freezers that gurgle and hum noisily when they're cooling your food.
A freezer needs to score 81% or more to be a Best Buy.
Should I buy it?
All of these tests contribute to a freezer’s overall Which? test score. The overall score doesn’t take price into account and is based on the following:
- 30% freezing speed
- 15% energy use
- 15% temperature stability
- 10% accuracy of recommended thermostat setting
- 10% ease of cleaning
- 10% ease of use
- 5% insulation
- 5% noise
A freezer needs to score 81% or more in our tough tests to qualify as a Best Buy. Freezers that score 45% or less are highlighted as Don’t Buy models to avoid.
Our reviews also reveal our expert verdict on whether we think each freezer is a good buy for its price.
Which? refrigeration testing
We constantly improve our freezer tests to ensure only the very best models are Best Buys. This means that newer models have been tested and rated in a slightly different way to older models - but you can still use the overall test scores to compare one freezer to another.
The section below outlines the key changes we’ve made to recent tests. You can see when each freeze was tested under the ‘Technical specification’ tab in each review.
Latest freezer tests – from 2015
In 2015, we overhauled the way we investigate how easy freezers are to use. Our new convenience tests assess how easy the drawers are to use and access, how simple the thermostat is to adjust and how loud and accurate any temperature alarm is.
Freezer running costs
We take into account the amount of power a freezer uses to freeze fresh food – to give you a more accurate idea of how each model might impact on your energy bills. Because our energy calculations are now more accurate, running costs for models tested before and after 2015 shouldn’t be directly compared.
Freezers tested before 2015
Our convenience and cleaning tests were based on visual assessments and an inventory of features.
We also used different methods of calculating running costs, which means these figures can be used as a rough guide to what you’ll pay and shouldn’t be compared. However, running costs don't contribute to the total test score, so this change doesn't influence performance ratings.
Want to see which freezers come top in our tests? Check out our Best Buy freezers.