Does AC affect the car engine?

In this blog, we find out answers to the following questions: Does AC affect the car engine? How to reduce the effects of air conditioning in a car? What factors can reduce the performance of the AC system in a car? How to maintain the air conditioning system in a car?

Does AC affect the car engine?

Yes, AC or air conditioning affects the car engine in the following ways:

  • Increase in fuel consumption
  • Increase in CO2 emissions
  • Reduced power output

Let’s take a closer look at both factors:

Increase in fuel consumption

The air conditioning system in a car uses a compressor to pressurize refrigerant gas. The compressor draws power from the engine when the air conditioning system is switched ON. Therefore, the engine cannot use its maximum power for propulsion.

When the air conditioning compressor is running, the engine control unit slightly increases the idle engine speed to prevent the internal combustion engine from stalling. Even at low engine speeds, the fuel consumption is higher than when the air conditioning is switched ON.

The outside temperature, cabin size of the car, and the set temperature by the driver play a massive role in the fuel consumption of the vehicle. Driving a car with the air conditioning system switched on and the interior temperature set to “LO” can increase fuel consumption by approximately 20-30 %.

Increase in CO2 emissions

Co2 emissions are the percentage of carbon dioxide or greenhouse gasses emitted by the vehicle. AC has a direct effect on the co2 emissions of a car, as more fuel is required to run the compressor. More fuel means more exhaust gasses and the emission of carbon dioxide.

Co2 or carbon dioxide is also a greenhouse gas, and an increase in the CO2 emissions of a car when AC is ON has an indirect effect on the environment. There are exhaust gas after-treatment systems in modern internal combustion engines to minimize the emissions but additional CO2 gasses are still present when the AC is ON.

Various studies suggest that CO2 emissions are increased by more than 10% when the car is in stop-and-go city traffic. An increase in the outside temperature will also result in the AC working for more periods to cool the cabin.

Reduced power output

When the internal combustion engine is running, ancillary components like the alternator, coolant water pump, and air conditioning compressor are driven by the crankshaft. Therefore, these components have a direct effect on the power output of the engine.

The air conditioning control unit controls the compressor via an electronic clutch, the compressor starts working when the clutch is engaged. If the engine is a small 3-4 cylinder with a displacement of fewer than 1.2 liters, the driver can suddenly feel reduced power when the compressor is ON.

If the engine is big then the reduction in power is not noticeable to the driver but the engine speed is slightly more compared to when the compressor is switched OFF. but if the mileage on the engine is high then the pressure of the compressor is more on the engine.

How to reduce the effects of air conditioning in a car?

The effects of AC in a car can be reduced in the following ways:

  • Avoid using AC when the outside temperature is not hot. The in-car temperature must be comfortable and not cold.
  • Use only the blower motor when the car is on the highway, and open the flow through the air flap if the vehicle is equipped with it.
  • Turn ON the recirculation mode or keep it on the auto setting. The recirculation mode will continue to recycle the already cold air through the cabin. The load on the AC is less and the temperature of the cabin is lower than the outside temperature.
  • There are aftermarket sunshades and reflectors available which can be installed behind the front windshield when the vehicle is parked. The in-car temperature will stay lower than the outside temperature.
  • Install a window tint on the car windows and at least 6 inches of tint on the front windshield. Window tint can lower the temperature inside a car significantly and the load on the AC is reduced.
  • Always use the temperature setting on the AC, set the temperature at 22-24 degree Celsius. The AC control unit will disengage the compressor as soon as the in-car temperature is within range.

AC will affect the car engine as long as the air conditioning compressor is connected to it. However, using these tips can help to minimize the ways AC affects the engine. Car manufacturers are also exploring different air conditioning systems to minimize the effects.

What factors can reduce the efficiency of the AC system in a car?

The following factors can reduce the efficiency of the AC system in a car:

  • Clogged AC filter

There is a dust filter and charcoal-activated AC filter in the air conditioning system of a car. It is used to filter the air entering the cabin from the recirculation flap. The filters also protect the blower motor from dust and foliage.

When the filters are clogged the air cooled by the evaporator coil is significantly less. The AC control unit in the car will keep the compressor running for a longer duration to cool the cabin. 

Therefore, replacing the AC filter at each service will help maintain the AC system’s efficiency. The dust filter may or may not be present in a car, it depends on the make and model.  

  • Faulty compressor

The air conditioning compressor is one of the most crucial components in the AC. if the compressor is faulty, the air does not get cold. Moreover, if there is a fault in the compressor pulley it will continue to draw power from the engine. 

A faulty compressor must be replaced as early as possible, fine metal particles can enter the components like the condenser and the expansion valve and cause further damage to the system.

  • Low refrigerant level

The level of the refrigerant gas in the air conditioning system must be according to the manufacturer’s specifications. If there is low refrigerant in the system then the temperature of the evaporator cannot go below 10 degrees Celsius.

The overall output of the air conditioning system is also reduced. Ideally, the refrigerant level does not reduce unless there is a leak. However, if the air-conditioning system is repaired, it can be refilled with the incorrect quantity of refrigerant.


This blog explained the different ways an AC affects car engines. Car makers are also implementing air conditioning compressors working on 48 V high voltage systems to reduce the load on the engine.