Why Opening The Refrigerator Won’t Actually Cool Down Your Home

A diagram showing a vapor-compression cycle and the four primary components: an evaporator, compressor, condenser, and expansion valve.

On a really hot summer day, chances are we’ve all thought about temporarily opening the refrigerator to cool down the surrounding area. In fact, whether sarcastically or not, many on social media have called this a “life hack” or “countryside engineering.” However, most of us are smart enough to keep the fridge door closed, as not only would keeping it open be much more expensive than just turning on air conditioning, it would likely also spoil the contents of the fridge.

While it’s true that it would be more expensive and spoil any perishables in the fridge, there is actually a bigger underlying reason for why opening the refrigerator to cool down the home, even if temporarily, is a bad idea. It all has to do with the basic concepts behind how refrigerators actually work. 

A refrigerator works by taking advantage of something called a vapor-compression cycle. There are four parts to this cycle: a compressor, a condenser coil, an expansion valve, and an evaporator coil. The process begins with the compressor, which pressurizes a refrigerant gas and raises its temperature. The refrigerant is very important because of its ability to change states easily between liquid and gas while absorbing and releasing heat. In the past, we used refrigerants like chlorofluorocarbons (CFCs), but nowadays, we’ve resorted to hydrofluorocarbons like R-134a to reduce environmental impact.

After going through the compressor, the refrigerant gas flows to the condenser coil, which is usually located at the back of the fridge. There, it releases heat to the surrounding air in the room as it condenses into a liquid. This heat release is why when you touch the back of a fridge, it feels very warm. The condenser works like a heat exchanger, transferring energy from the hot refrigerant to the cooler room air. 

Next, the refrigerant, now a liquid, passes through the expansion valve, also referred to as a throttle valve or metering device. This valve reduces the refrigerant’s pressure suddenly, which causes it to expand and evaporate in the evaporator coil inside the fridge. As it evaporates, it absorbs heat from the interior, cooling the air and contents inside the fridge. The evaporator is another heat exchanger, designed to pull heat from the fridge’s low-temperature space. The cycle repeats as the now-gaseous refrigerant returns to the compressor. This closed loop keeps the refrigerant circulating without needing to add more, thus making the system self-contained.

The back part of a fridge, exposing its looping refrigerator coils.

Over time, the evaporator might collect ice or water from humidity in the fridge air. However, modern fridges have automatic defrost cycles to melt this buildup. The liquid water, as the buildup melts, is drained into a pan, where it evaporates or gets carried away. 

The key point we’re trying to make here is that the refrigerator simply moves heat from inside to outside. It doesn’t just magically create cold air. When heat is absorbed from inside the fridge, it is released outside, into the room. Including the extra heat from the compressor’s electrical work, which also gets released into the surrounding area outside the fridge, it adds up. This makes the system inefficient for cooling the room. The coefficient of performance (COP) for a typical household fridge is around 2 to 3. What this means is that for every unit of electrical energy used, the fridge removes about 2 to 3 units of heat from the inside. The total heat added to the room will not only include the heat removed from the inside but also the electrical energy input. As a result, the net effect is always warming the room slightly, even with the door closed. This follows the first law of thermodynamics, which states that energy is conserved. The electrical input “W” plus the heat pulled from inside “Qc” equals the total heat dumped outside “Qh.” We can express this as an equation: 

Qh = W + Qc

According to the second law of thermodynamics, you cannot transfer heat from a colder body to a hotter one without adding work, and some of that work always turns into waste heat. This is why fridges can never be 100% efficient, as the COP would always be less than what an ideal thermodynamic cycle would allow. For fridge temperatures, this might ideally be around 5 to 6, but real systems fall short due to losses in compression, friction, and heat transfer.

If you open the door, cold air will spill out at first because it is denser than the warmer room air. This will give a short cooling effect, and at best, it might drop the ambient temperature by a degree or two for a few minutes. But the fridge will then run harder to cool its interior as warmer air enters through the open door. Warm air will rush in to replace the cold air, raising the inside temperature and triggering the fridge’s internal thermostat. The compressor will kick on more frequently or stay on for longer. The heat released at the condenser coil will outweigh the initial cold air release, and over time, the room temperature will end up rising instead of falling. Studies and simple experiments show that after an hour or so, the room can warm by 0.5°C to 1.0°C more than if the door had stayed closed.

Again, this ties back into the first law of thermodynamics: with the door open, the inside and outside become one space, so the fridge will just be pumping heat around in a circle while adding electrical energy as extra heat. The compressor, condenser, and other parts generate friction and resistance, converting some electricity directly to warmth. If the room is sealed, the only energy input will be from the wall outlet, so the total heat will build up.

Air conditioning units avoid this counteractive heating effect by placing the condenser outside of the home. They pump heat directly to the outdoors, allowing net cooling indoors. The evaporator stays inside for cooling, while the hot side vents to the atmosphere. A fridge with the door open doesn’t have this kind of separation, so it heats the space it occupies. In fact, even a closed fridge adds a tiny bit of heat to the kitchen over time due to its inefficiency, but opening the door amplifies this by making the cycle pointless and continuous. The second law of thermodynamics ensures no system can move heat perfectly without some waste, so the electrical input always contributes extra warmth. Therefore, if you feel the need to cool down your home, opening the refrigerator door is actually one of the worst things you can do!