Fridge at 4°C and freezer at -18°C: the bill nobody measures

Fridge at 4°C and freezer at -18°C: the bill nobody measures

A digital thermometer of the kind sold online for aquariums and freezers, with a measurement range of -50 to +70 degrees, costs less than two coffees. With that device in hand, the question many people finally ask is a concrete one: what temperature should the fridge and freezer be set at so you don't overpay on your electricity bill? The official answer circulating in consumer guides puts the freezer at -18°C and the fridge between 2°C and 4°C. And that's where the confusion begins.

The fridge at 4°C: the number that doesn't convince everyone

The technical consensus exists and is easy to find: -18°C for the freezer and a range of 2°C to 4°C for the fridge. It's what food storage guides repeat and what's printed on most household thermostats. So far, nothing to argue with.

The problem is that theory clashes with the practice of anyone who looks at the energy label and does the math. Some argue that 2°C-4°C is too low and that raising it a couple of degrees is enough to make the compressor kick in less often. The logic is simple: the less often the motor starts up, the less it consumes. And the motor accounts for the largest share of the bill.

The reasonable doubt: how much do you actually save by raising the temperature one degree? The short answer is that it depends on the appliance, the insulation and how often the door is peine. The long answer requires measuring, and measuring is precisely what almost nobody does.

How much the compressor uses when it's not running

Here comes the surprising figure. With a power meter plugged into the fridge, the difference between keeping it at 5°C and at 6°C was a mere 0.5 watts in instantaneous consumption, always with the compressor off. In other words, practically nothing. The real cost isn't in the thermostat setting, it's in the number of hours the motor spends running.

The same experiment turned up another curiosity: opening the fridge door raises consumption by about 20 watts because of the interior light. This doesn't happen with the freezer, because it has none. Opening and closing the fridge without thinking costs more than the automatic gesture suggests.

The aquarium thermometer that works for the fridge

The tool that has brought the issue to the table is an LCD digital thermometer of the kind sold for aquariums and freezers, with a range of -50 to +70 degrees. It's cheap and does exactly what it's meant to do: tell you the actual temperature inside, not the one the dial shows.

Because the dial lies. The numbers on the thermostat (1, 2, 3, 4, 5, 6) aren't degrees, they're positions on an internal scale. One fridge with the dial at minimum might be at 8°C while another with the same setting is at 4°C. Without a separate thermometer, you're adjusting blind.

The freezer at -18°C and the enzyme limit

-18°C isn't arbitrary. At that temperature the enzymatic activity in food slows down, but doesn't stop entirely. Degradation continues, very slowly, which is why frozen meat doesn't last forever even when it's hard as a rock. It's a warning for anyone who treats the freezer as an infinite pantry.

Therein lies the awkward trade-off: lowering the temperature further protects food better but drives up consumption; raising it saves euros and shortens the shelf life of what you store. There's no single answer, and anyone claiming otherwise is selling something.

What is clear is that most household fridges have been running for years with the thermostat at a setting nobody has ever checked. A three-euro device and a free afternoon are enough to find out whether you're overpaying. The open question is how many people will keep adjusting by eye.