Does the car consume more with the air conditioning on?

Summer is synonymous with running the air conditioning, so we reveal whether the car consumes more petrol or battery in the case of electric cars.

Summer arrives and with it the high temperatures, so getting stuck in a traffic jam at 40 degrees leaves no alternative but to switch on the air conditioning in our car if we don’t want to arrive at our destination dripping with sweat.

That cool breeze coming out of the ventilation ducts is a real blessing but, if you’re curious, you may have wondered this: does the car use more petrol if we have the air conditioning on? Since at Tech y Motor we are, we’re going to give you an answer.

However, before knowing whether it uses more or not, we must understand how the air conditioning works. This system is made up of three fundamental components: evaporator, condenser and compressor.

The compressor, as its name suggests, compresses a refrigerant gas which expands in the evaporator, thereby producing cold, and then condenses in the condenser, thereby producing heat. The air conditioning makes use of the ventilation circuit and incorporates the evaporator (where the cold is produced), while the condenser (which heats up) sends the air outside. Thanks to this, the air is cooled before entering the cabin.

Does air conditioning consume fuel?

Once this question is cleared up, we can explain whether the system drinks from our tank or not. The air conditioning compressor in our home runs on electricity, but in a car, since there is no mains electricity, it is connected to the petrol engine through a system of pulleys that can be engaged and disengaged.

When we press the A/C button, we often notice a slight jolt from the engine. This is because the compressor engages with the engine to operate, which represents a small load on the combustion engine. Because of this, the driver has to press the accelerator pedal harder to extract the same power, so we already have the answer: the engine does use more.

How much more does the car use?

Right, we now have the affirmative answer, but let’s go a bit deeper: how much more does the car consume when we switch on the air conditioning? The compressor consumes between 1.1 and 3.9 kW, and one horsepower equals 0.736 kW. This means that when we activate it, this device takes away between 1.5 and 5.3 horsepower depending on how hot it is.

Taking these figures into account and at an average speed of 100 km/h, air conditioning consumption would increase by between 0.29 and 1.02 litres per 100 km. However, there may be variations depending on the size of a car’s compressor, since the one fitted to a Citroën Saxo has little in common with that of a Mercedes Class G.

The new mild-hybrid cars have solved this additional consumption. In these, the starter motor acts as a small electric motor, recovering energy during braking and deceleration, although it can never drive the car on its own. This energy is used to power the car’s auxiliary systems, including the air conditioning, so the compressor does not depend on the combustion engine and consumption does not change. If you want to know more about mild hybrids, here we explain how they work in detail.

And what about an electric car?

The difference in an electric car is that the air conditioning system is powered directly by the traction battery, so as you can imagine, it considerably reduces range.

The compressor cannot be powered in the same way as in a combustion engine, since that is always running when we have the system switched on, whereas an electric motor is not always running. For this reason, the compressor in an electric car has a small electric motor to keep it running, which operates thanks to the traction battery. The same arrangement applies in hybrid and plug-in hybrid cars, although it is less significant in these because they have the backup of the combustion engine.

Furthermore, in an electric car, the air conditioning is also used to cool the batteries, so its use is greater. Therefore, depending on the outside temperature and what we demand of it, the air conditioning in an electric car can reduce total range by up to 10%.

In addition, an electric motor does not produce the residual heat that a combustion engine does. Therefore, electric cars have heating elements that take care of warming the fluid running through the circuit. As a result, electric cars often consume more when heating the air than when cooling it.

It is true that manufacturers know these heating elements use a lot of range, which is why some models such as the Nissan Leaf or the Renault ZOE have replaced them with much more efficient heat pumps. Furthermore, consumption in this type of car can be reduced by using one-pedal driving.

So, if this question has been on your mind for some time, don’t give it another thought: your car does use more when you switch on the air conditioning. However, seeing that the increase will be 1 litre at most, provided it works properly thanks to, for example, following our tips for always keeping the air conditioning in good condition, it is worth using it rather than suffocating in the heat.