Last updated on November 27th, 2023
When it comes to setting the temperature for your fridge, the general consensus is colder than 5°C for optimal food safety. However, the reality is a bit more nuanced. Most domestic fridges allow you to adjust temperatures between 1°C and 9°C in the fridge and -10°C to -20°C in the freezer. So, why the range?
How Cold Should a Fridge Be?
Ideal Temperature: Less than 5°C
Real-world Recommendation: 3°C
Food Standards Australia New Zealand recommends keeping your fridge below 5°C for optimum food safety and to prevent the growth of food-poisoning bacteria. However, due to factors like varying temperatures within the fridge and fluctuations, setting it to around 3°C on the top shelf is usually the sweet spot.
The fridge is not a static environment; it maintains an average temperature not a precise one. Rather than consistently holding a specific temperature like 3°C, it might fluctuate between 1°C and 5°C.
Hot Air Rises
Another compounding factor is the simple fact that hot air rises and cold air sinks. So while the temperature of the fridge is dynamic, it is also usually warmer on the top shelf and colder on the bottom shelf. So while the top shelf may be varying between 1-5 degrees, the vegetable crisper might be 0-4 degrees, or worse -1-3°C. So your nice lettuce is freezing and thawing several times a day into a soggy mess. It’s good advice to store the perishable groceries like meat, fish, juice and dairy closer to the bottom of the fridge, with condiments and non-perishables closer to the top. 3°C on the top shelf should mean the top shelf never goes above 5°C while the contents of the vegetable crisper don’t freeze.
You Get What You Pay For!
Fridge temperature fluctuation is influenced by factors such as the frequency of door openings, how loaded it is, external temperature, and the capacity of the fridge’s cooling system. Better fridges have less fluctuation and often you get what you pay for. Fisher and Paykel fridges for example can, and often do, run their fans independently of the compressor to circulate the air for a more consistent and stable temperature throughout. A cheaper fridge won’t do this. A better fridge would be expected to have 1°C or less of fluctuation from the average, and less than 1°C of difference between the top and bottom shelf, while a cheaper fridge could expect to see 2°C or more of fluctuation.
Why the Range?
If there’s really only one correct temperature for your fridge, then why do manufacturers bother to give you the ability to adjust it? Wouldn’t it be better if there was no need for you to have to google this dumb information and your fridge was just set at the correct, safe, temperature already? Honestly yes, but it’s not practical. Other sources will give you bad answers – wanting to save energy, or storing cold sensitive items at a warmer temperature.
The real reason is that over time thermostats and sensors, go out of their factory range. The same setting on one would be a slightly different temperature to another, and with time and entropy, as springs lose their tension, and corrosion creeps in things go out of whack. The setting that used to be 3°C is now 4°C or 2°C, and without the ability to make an adjustment your fridge isn’t running where it should be, significantly reducing its service life.
How Cold Should a Freezer Be?
Ideal Temperature: -18°C or colder
The freezer’s primary role is to keep food frozen, preserving it for extended periods. The ideal temperature for the freezer compartment is -18°C or lower. This temperature is cold enough to prevent the growth of bacteria, yeast, and mould, ensuring the long-term preservation of your frozen goods. Setting the temperature at -18°C or colder helps maintain the quality, texture, and flavour of the frozen items. Food is less prone to freezer burn, and less subject to degradation caused by enzymes in the food. On the downside running your freezer this cold will mean it costs more to run, and will have a shorter service life than if you ran it hotter, simply due to wear and tear on the mechanical systems being on longer.
Adjusting for Practicality
Having adjustability in the freezer makes more sense, because it really depends on how an individual user wants to go about things. A classic example is ice cream. If you want to store the ice cream the right temperature is colder than -18°C. But ice cream that cold is not fun to eat, it is rock hard. Your spoon has bent trying to scoop it out of the punnet, and then you have to wait 10 minutes for it to thaw out enough to eat. But the thing is it doesn’t thaw consistently, the outside melts while the inside stays a frozen solid core. If you just bought icecream, you plan on eating it in the next week and you want it to be nice and creamy and delicious all the way through, you want your freezer set at around -12°C, the perfect ice cream eating temperature.
You might also want to save some money, and running your freezer warmer will save you money. Do you want to eat that spaghetti bolognaise you made in the next three weeks or the next 3 months? If you want to store your food longer, you want to keep it colder. But if nothing stays in your freezer for more than a few weeks, you don’t need it very cold. The general consensus seems to be that if you keep your freezer at or below -18°C it will be safe to eat indefinitely, but after 3-12 months depending on what it is, the flavour and texture will begin to suffer.
Freezer Size Matters
If you have a fridge with a smaller freezer, like the 248L Fisher and Paykel, generally you need to run the freezer colder. Most domestic fridges I’ve seen max out at -20°C in the freezer. As a general rule I’d say anything below 300L total capacity should be run pretty cold in the freezer. This is because during the defrost cycle, where a heater turns on in the back of every frost free fridge for about 20 minutes every 1-2 days, the contents of a little freezer just don’t have the thermal mass to stay frozen, especially if its pretty empty. If they’re not very frozen at the start of the defrost cycle, there’s a good chance they will have thawed out by the end of it. One of the most common symptoms of this is ice cream that has melted and then frozen solid like an ice block.
A couple of other considerations are the fridge quality and how often the freezer door will be opened. If it’s a cheap appliance from an unknown brand you might expect more temperature fluctuations and to make sure it’s not getting too warm, you need to set it colder. If you have kids constantly opening the freezer door in the middle of Summer to get to the icy poles again, better to set it colder as the more the door is opened, especially on a hot day the more the freezer temperature will fluctuate. If you’re worried about the power going out setting your freezer colder makes sense as well since the colder it is when the power goes out, the more likely it is you will make it through the blackout with the contents of your freezer still frozen.