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Does Running the AC in Your Car Use More Gas?

Dhanashree Patane
Saving gas and still trying to keep your cool when traveling during the hot summer months need not be a balancing act, especially when you avoid flipping the AC to full thrust for a cool wisp of air in your car. Find out if running the AC in your car consumes more gas.

Quick Fact

According to the Society of Automotive Engineers, on an average, the fuel consumption goes up by 5 to 10 percent if the AC is on, whereas, when driving at speeds of more than 55 miles per hour (88.5 kilometers approx. per hour), with the windows rolled down, gas consumption increases by almost 20 percent.
Today, with the price of gas scaling new heights, most people would go an extra mile to increase the mileage of their car. Saving gas is not only beneficial on your pocket, but also to the environment. So, in a bid to save gas, most people do not use the AC in the car. And this, perhaps, seems to be the easiest way to save gas? But is it really?
Most people believe more gas is consumed when the car is driven with its windows rolled down and the AC on. Well, it is true. But, it is also true that gas is also not saved with the windows down and AC off. Here is a quick disclosure of whether using the AC in the car affects the mileage and gas consumption. Let us take a look.

Does Using the AC in Your Car Consume More Gas?
◢ Most people believe that using an AC in the car reduces mileage, which, to a certain extent is true. Cooling in the car takes place with the help of energy drawn from the engine, which uses fuel, which, in turn, may increase gas consumption.
◢ We could say there are two considerations when it comes to the use of air conditioning and saving gas. Firstly, it depends on the make of the car and how the compressor in your car works. The second factor to consider is called drag, or the change in air dynamics inside and outside the car, which in simple terms, can be called air resistance.
◢ Air resistance or drag, is the resistance created by air, when the car travels at any speed. Drag is encountered by all moving objects. Due to drag (air resistance), the engine has to supply more energy for the car to travel.
◢ Most cars today have an aerodynamic design. This helps the car easily cut through the air, with minimal resistance.
However, even in an aerodynamic design, if the windows are rolled down, the air easily enters the car and creates resistance, which affects the fuel consumption, as here again the engine has to pump extra energy to overcome this resistance and maintain speed.
◢ If the windows of the car were rolled up, the car gives no space for the wind to travel in, so the wind cuts from above the car, which creates lesser resistance, and, in turn, avoids extra work for the engine.
◢ So, even when you are driving without the AC on to save fuel, rolling down the windows will create drag or air resistance. So here, again, there is going to be more work for the engine to pump energy and force, using extra gas.
In some cases, the drag is so powerful, that it takes more fuel to supply energy and speed with the windows rolled down, than it would take to drive with the AC running.
◢ Much research has been conducted to find what is best for the mileage of automobiles―AC on or not. Many have zeroed in to what we can now call a thumb rule. Whenever you are in traffic, roll down the windows. Switch on the AC when you are driving on the highway.
◢ To simplify, using the AC when the car is at a higher speed is a good option, as it will not burn excess fuel. Whereas, when driving at a lower speed and in traffic, one can roll down the windows whenever possible.
◢ According to the Society of Automotive Engineers, on an average the fuel consumption goes up by 5 to 10 percent if the AC is on, whereas, when driving at speeds of more than 55 miles per hour (88.5 kilometers approx. per hour), with the windows rolled down, fuel consumption increases by almost 20 percent.
◢ So, we could say that the best bet is driving at low speeds with the windows down, and at high speeds one can turn the cooling system on. To save gas, alter the use of AC, according to the mentioned guidelines. It is wise to know when you really 'need' the AC on, and when it is OK to leave the windows rolled down.
Does running the AC in a car increase gas consumption? A very direct answer is 'yes' it does, there is no denying that the engine does need extra fuel to power cooling. But, other factors like air resistance (drag) created when the windows are rolled down, also increase the gas consumption of the car.
So, the best advice would be to make a smart choice, alter the use of the AC in the car. Save on gas and get come coolness too!