Your fridge should sit at around 3 to 5C and your freezer at about -18C. Get those two numbers right and you keep food safe while spending as little as possible, because a fridge-freezer is one of the few appliances that never switches off, so anything you overpay you overpay around the clock. The trouble is that most people set it by a numbered dial that tells you nothing about the actual temperature, and quite a few homes run the fridge several degrees colder than it needs to be, paying for cooling that does no good. This page covers the right settings, why colder costs more, and the handful of habits that keep the bill down.
The short answer. Aim for a fridge at 5C or below, with about 3 to 4C a sensible target, and a freezer at -18C. The Food Standards Agency puts the safe fridge line at 5C. Setting either compartment colder than that does not keep food any safer, it just runs the compressor more and costs you more. Because the appliance is on every hour of the year, a dial set too cold is a small leak that never stops.
Free download
Grab the Home Energy-Saving Checklist
A plain, one-page checklist of the moves that actually cut a UK bill, worked against the current £1,723 Ofgem cap at 26.32p a unit. No fluff, no gadgets to buy. Pop your email in and it lands in your inbox, along with the odd no-nonsense tip.
Free, one click to unsubscribe. The download starts the moment you sign up.
The right numbers, and why they are the right numbers
Food safety sets the fridge target. Chilled food stays safe and lasts longest between about 0C and 5C, because that range is cold enough to slow the bacteria that spoil food and make people ill, without freezing the contents. The official line is 5C or below, so aiming for 3 to 4C gives you a small margin for the door being opened and warm shopping going in, while staying clear of the point where salad and milk start to freeze at the back. For the freezer, -18C is the long-standing standard: it holds food safely for months and stops the slow quality loss that happens at warmer freezer temperatures. Going colder than -18C, say to -22C or -24C, does not make frozen food any safer or last meaningfully longer, but it does make the appliance work harder.
Why colder costs more, every hour
A fridge does not make cold; it moves heat out of the cabinet and dumps it into the room, and the compressor that does the work uses electricity every time it runs. The bigger the gap between the inside of the fridge and the room around it, the harder and more often the compressor runs to hold that gap. So a fridge set to 2C in a 20C kitchen has to shift more heat than the same fridge set to 4C, and it does that not once but continuously, day and night, all year. As a rough rule of thumb, each degree colder than necessary adds a few per cent to the running cost. That sounds trivial until you remember it applies to an appliance that is never off. A fridge-freezer using an example 250 kWh a year costs about £65 at the current cap rate of 26.32p per kWh; nudge it several degrees colder than it needs and you can add a fiver or more a year for food that is no better kept. It is a small number, but it is a small number you pay forever.
The dial that tells you almost nothing
Here is where most homes go wrong. A lot of fridges, especially older ones, have a dial marked 1 to 5 or 1 to 7, with no temperatures on it at all. People reasonably assume a higher number means warmer, when in fact the number sets how hard the fridge works, so a higher number means colder. Set it to 5 out of 5 thinking you are being gentle and you have actually put it on maximum cooling, running the compressor flat out and freezing your lettuce. Even where a dial does show a rough scale, it rarely reflects the real temperature inside, which depends on how full the fridge is, how warm the kitchen is and how often the door opens. Treat the dial as a control to adjust, not as a readout to trust, and set it by measuring the result rather than by the number.
How to check the real temperature
Measuring is easy and worth doing once. A cheap fridge thermometer, the dial or digital kind sold for a few pounds, does the job. The reliable trick is to stand a glass of water in the middle of the fridge, leave it overnight, and read the thermometer in the water in the morning. Using water rather than air gives a steady reading that ignores the brief warm-up every time the door opens, so you see the true working temperature. If it reads above 5C, turn the dial to a colder setting, wait a day, and check again. If it reads down at 1 or 2C, you are running colder than you need, so back the dial off a notch and save the difference. Do the same in the freezer with a freezer thermometer, aiming for -18C. It takes two mornings and sets the appliance right for years. If you want to see what your fridge actually draws while you are at it, a plug-in monitor as covered in using a plug-in energy monitor shows the consumption directly, and the running cost calculator turns that into a yearly figure.
Where you put it matters as much as the dial
The room around the fridge decides how hard it has to work, so placement is part of the setting. A fridge standing next to the oven, beside a radiator or in a patch of direct sun has to fight that heat all day, running the compressor more to hold the same internal temperature. Give it a cooler spot if you can, and leave a gap behind and above it so the warm air coming off the coils can escape rather than pooling against the wall; a fridge boxed tightly into a cupboard with no ventilation runs hotter and costs more. Keep the coils at the back reasonably free of dust for the same reason. Ambient temperature also explains a common surprise with a fridge or freezer kept in a garage or outbuilding: in a cold winter garage a fridge may barely run, but many appliances are not rated for very cold surroundings and can behave oddly, and in a hot summer garage the same appliance works overtime. In a heatwave any fridge-freezer struggles, which the fridge and freezer in hot weather guide covers in detail.
Packing, airflow and the door
How you load the fridge changes how efficiently it holds its temperature. A reasonably full fridge keeps cold better than an empty one, because the chilled food acts as a store of cold that steadies the temperature between compressor cycles, though you should not pack it so tight that air cannot circulate around the shelves. The freezer is clearer still: a full freezer runs more efficiently than a half-empty one, so if yours is sparse, filling the gaps with bottles of water is a genuinely useful trick. The door is the other daily factor. Every time it opens, cold air falls out and warm room air replaces it, so the compressor kicks in to recover. Opening it less, deciding what you want before you open it, and never holding the door open while you dither all trim the work. And letting hot leftovers cool to room temperature before they go in stops you dumping a load of heat straight into the cabinet.
Seals, frost and keeping it honest
A few maintenance points keep an efficient setting efficient. The door seal is the one people ignore: a perished or grubby rubber seal lets cold leak out continuously, so the fridge runs more to make up for it. Test it by shutting the door on a sheet of paper; if the paper slides out easily the seal is not gripping and wants cleaning or replacing. Frost is the freezer equivalent. A thick layer of ice on the walls of a freezer acts as insulation in the wrong place and forces the appliance to work harder, so if yours is not frost-free, defrosting it once the ice builds past a few millimetres restores its efficiency. None of this changes the temperature you should aim for, but all of it decides how much electricity the appliance burns hitting that temperature. For the wider question of whether an old, thirsty fridge-freezer is worth replacing at all, the fridge and freezer efficiency guide works through the payback.
What I would actually do
Buy a fridge thermometer, stand a glass of water in the fridge overnight, and set the dial so the water reads 3 to 4C, then do the same for the freezer at -18C. That one check catches the most common and most pointless waste, a fridge run far colder than it needs because the dial was a mystery. After that, keep it out of the sun and away from the oven, leave it room to breathe, keep the seal clean and the freezer reasonably full and free of thick frost, and open the door with a bit of purpose. Because a fridge-freezer is always on, it is one of the appliances worth getting right once, and it sits near the top of the list in what uses the most electricity in your home precisely because it never stops. Set it properly and it quietly costs you the least it can, year after year.
Common questions
What temperature should a fridge be?
Between 0C and 5C, with about 3 to 4C a good target. The Food Standards Agency puts the safe line at 5C or below. That range keeps food safe and slows spoilage without freezing salad and milk at the back of the shelf.
What temperature should a freezer be?
-18C is the standard, and it holds frozen food safely for months. Setting it colder, to -22C or below, does not keep food any safer or noticeably longer; it just makes the appliance run more and cost more.
Does turning the fridge colder use more electricity?
Yes. The colder you set it relative to the room, the harder and more often the compressor runs, so a fridge set to 2C uses more than the same fridge at 4C. As a rough guide each unnecessary degree colder adds a few per cent to the running cost, and because a fridge is never off, that adds up over a year.
On a fridge dial from 1 to 5, which number is coldest?
The highest number is usually the coldest, because the dial sets how hard the fridge works rather than the temperature directly. Setting it to 5 runs the compressor hardest. The reliable way to get it right is to ignore the number and measure the actual temperature with a fridge thermometer in a glass of water.