Fuel consumption is an essential topic for any driver. Especially in the summer, when long-distance trips are planned.
Given that modern cars are completed with air conditioning and climate installations, which are based on air-conditioning, raises the question about the impact of air conditioning on fuel consumption and acceleration dynamics of the vehicle.
The same topic is regularly discussed on the forums dedicated to cars. There are questions about fuel consumption and impact on the consumption of the inclusion of additional devices, such as an air conditioner.
Does the air conditioner increase fuel consumption or not?
Of course, the inclusion of a/c (as well as any other attachments having a drive from the motor) increases fuel consumption.
Moreover, any motorist can notice that while parked with the engine on the switching on and off, the air conditioner changes the number of engine revs, which is clearly noticeable on the tachometer.
Vehicles equipped with an onboard trip computer allow you to see an increase in fuel consumption when the air conditioner is turned on, see Table 1.
The increase in fuel consumption when the air conditioner is turned on
|Mode||Fuel consumption, l/h|
|Warmed up engine, a/c off||0.6|
|Warmed up engine, a/c on||1.1|
As seen in Table 1, the air conditioning increases fuel consumption by 0.5 l/hr.
Of course, when driving in a “traffic jam” when the engine is operating in the most unfavorable mode, the inclusion of air conditioning reduces fuel efficiency.
Why is the fuel consumption increase is not noticeable when driving on the highway?
Table 1 shows that the air conditioner consumes 0.5 l/hr. Assume that the fuel consumption on the air conditioner is in uniform motion is still the same 0.5 liters per hour. Then, with the uniform movement of the vehicle at a speed of 100 km/h, the turned-on air conditioner will give an equal increase in fuel consumption of 0.5 l/hr.
In other words, fuel consumption during the uniform motion on the highway should increase by 0.5 l/100 km.
This is the maximum fuel consumption due to the operation of the air conditioner.
In fact, the movement of the highway has a somewhat different character. In economical driving, the driver pulls under the speed limit signs (to intersections, etc.) with the gas pedal released and instant fuel consumption of 0 liters/100 km. Thus, while driving on the highway in economical mode, a/c adds to fuel consumption less than 0.5 l/100 km. On average, it turns out that the air conditioner adds (depending on the terrain of the highway, the number of overtaking, and other factors) 0.2-0.3 rarely 0.4 l/100 km.
Such fuel consumption values are at the limit of practical measuring accuracy and are often masked by other factors, see Table 2.
Fuel consumption, car load and the character of motion
|Character of motion||Car loading||A/C||Fuel consumption, l/100 km|
|Economical||Driver and passenger||On||5.9-6.1|
|Dynamic||Driver and passenger||On||6.5-7.4|
For example, a trip with the driver and the passenger when the air conditioner is on (the track and route are the same) is accompanied by average fuel consumption of 5.9-6.1 liters/100 km.
The ride without passengers when the air conditioner is on (the track and the route are the same) is accompanied by average fuel consumption of 5.7-5.9 liters/100 km.
The ride without passengers with A/C off (the track and the route are the same) is accompanied by average fuel consumption of 5.6-5.7 liters/100 km.
Dynamic driving on the same track and the same route with a driver and a passenger when the air conditioner turned on is accompanied by the average fuel consumption of 6.5-7.4 liters/100 km.
Analyzing Table 2, it is easy to notice that the style of driving of the car and its load have a more significant impact on the amount of fuel consumption than the operation of an air conditioner or climate system.
Therefore, in most cases, the switching on of the a/c when driving on the highway does not affect the measured fuel consumption because other factors mask it.
How does air conditioning work affect acceleration dynamics?
How does the operation of the air conditioner affect the acceleration dynamics of the car? Of course, negatively.
Air Conditioning uses part of the engine’s power during its operation. Maintaining uniform motion in traffic with speeds allowed by the “Traffic Rules” does not require all engine power, so some of the power can be spent on the operation of the air conditioner.
During intensive acceleration, the driver needs all the power of the engine, so the deterioration of the acceleration dynamics of the car becomes noticeable with the air conditioner turned on. On low-power engines, it is especially noticeable.
Operation of cars with engine capacity of less than 100 hp showed that during intensive overtaking, especially uphill, air conditioning is best to turn off, then the car will have at least some dynamics.
In more powerful cars (with an engine power of more than 100 hp), the operation of the air conditioning system does not have such a significant influence on dynamics, or at least, this effect is not so noticeable.
Summarizing we can say that:
- Turned on air conditioner increases the fuel consumption of the vehicle. However, this does not mean that the use of the air conditioner should be abandoned;
- The increase in fuel consumption from the working air conditioning when driving is insignificant and often is within the measurement error or is masked by other factors;
- A working air conditioner affects fuel consumption (fuel consumption increases) to a lesser extent than a vehicle load;
- A dynamic driving style significantly increases overall fuel consumption;
- Economical driving reduces the overall fuel consumption even when the air conditioner is on;
- The operating air conditioner reduces the acceleration dynamics of the car. To a greater extent, this is noticeable on cars with an engine power of less than 100 hp.
Ways to save fuel in the summer with working air conditioner
There are some simple yet effective ways to save fuel in the summer, even with the possibility of turning on the air conditioner. Thus, in traffic jams or at low speeds, it is better not to use the air conditioner, and instead open the windows, and at high – on the contrary, close the windows if possible, and turn on the air conditioning.
It should be remembered that the air conditioning temperature you set must not be lower than 5 degrees to that on the street – thanks to this, you not only will save fuel but also protect yourself from sudden temperature changes. Also, do not use the air conditioner when the vehicle is stationary – engine idle speed, in this case, increases the load and, accordingly, the engine begins to consume more fuel.