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It is obvious that your car’s gas mileage is affected when an air conditioner is running. In terms of consuming gas, your car’s air conditioner is not much different from other features. But how much gas does AC use? In this post, we are going to explain it. 

How car AC works

No matter what type of car you have, air conditioning works pretty much the same way. Refrigerant, a high pressure gas is used to run the systems. Here are the main parts of the air conditioning system: 

Compressor: This part is used to liquefy the refrigerant. As a result, the condenser gets the refrigerant. 

Condenser: This part cools the refrigerant and sends it to the orifice tube or expansion valve. 

Orifice tube or expansion valve: It turns the refrigerant into a gas again and moves it to the accumulator or receiver. 

Accumulator or receiver: The function of this part is to dry up the refrigerant. Dense refrigerant is transferred to the last part, the evaporator. 

Evaporator: The heat is transferred to the refrigerant and the evaporator makes it happen. 

How much gas is used?

The amount of gas used to run a car’s AC depends on the operation of the compressor. On a summer day, air conditioners can decrease the gas mileage up to 5%. The air conditioner will use up more gas if the car has more passengers. 

For example, if you are driving a car with a 90 HP engine run by gas, the engine will consume about 500 ml of gas after running about 100 kilometers. But if your car is sitting idle but the air conditioning is on, the car will consume a lot of gas. To sum it up, the faster you drive the less gas the air conditioner will use.

For the mileage, keeping the windows open is bad when you are driving the car at 50 miles per hour. When the windows are open, fuel efficiency significantly drops. Several factors such as the cost, speed, model and driving conditions determine mileage efficiency. 

Running your car’s AC 

Your car’s AC can be really useful when it is hot outside. But gas prices are getting higher, and people are trying to find ways to reduce gas usage. As a car owner, you may take fuel economy seriously. Most of us seem to know it for sure that a car uses more gas when the AC is running.

But this is not true in all cases. If you are running a fuel-efficient car, running the air conditioner will not make a huge difference. It is true that the air conditioner receives power from the engine, and the engine produces energy by consuming gas. But does that mean that an air conditioner uses a significant amount of gas? How much gas does AC use?

As we will discuss it later, to some extent it depends on the type and model of your car. In some vehicles, the AC uses a significant amount of gas, resulting in a 20% decrease in fuel economy.

But leaving the AC idle is not a very effective way to save gas. If you roll the windows down, it will create a drag effect, which will cause the engine to work harder. And as a result, your car will end up using more gas.

Can it be fuel-efficient?

Your car’s AC uses relatively less gas when you are driving the car fast. And it uses more gas when the windows are left open. Aerodynamic drag is elevated when the windows are open. The engine burns more fuel when it works harder. 

You can keep the windows up when running the air conditioner. Another choice is to stop using the air conditioner. Just turn it off. But before you do it, ask the question again: how much gas does AC use? The answer is: not much. Keeping your AC idle is your choice, although not a very good choice.

When the air conditioner is running, power is being siphoned away from the engine. To keep the feature going, your car must use more fuel. When the windows are down, drag effect is created and as a result your car has to work harder to maintain the same speed. 

There are a few other things you can do to improve fuel economy. You can brake gradually and pack light. The tires should be inflated and aligned properly. Avoid using cheap oil and avoid parking the car in a sunny spot. And if that is not possible, consider using sun reflectors. 

Making a choice: AC on versus windows down

Different organizations have tried both methods and reached nearly similar conclusions. A number of tests have been conducted by the Society of Automotive Engineers. When you are driving your car on a city street, it is good to drive with the Windows down, according to a recommendation by Stanford University.

How much gas does AC use? It depends on your car, but in most cases the air conditioner will use less gas if the speed of the car is above 45 miles per hour. Your car’s fuel efficiency is affected by multiple factors. Depending on the size and age of your car, the AC can use up to 1 gallon of gas per every 3 miles. That means, a running AC significantly lowers your car’s fuel efficiency.

So, should you roll down the windows? The answer is not straightforward, because rolling down the windows also has a negative effect: it can create a drag effect. As a result, your car works harder and uses more fuel.

To reduce gas consumption, it may be a good idea to drive your car early in the morning, because this part of the day is relatively cool. The most effective way to reduce fuel consumption is to drive your car with the Windows down and the air conditioner off. 

Additional tips for balancing gas consumption

The tips below will help you reduce gas consumption while keeping the air conditioner functional. 

  • Air conditioner should be used wisely, because it burns up gas. If the outside temperatures are pleasant, keep the windows open. It is possible to maintain a comfortable air flow by using the vent. 
  • The hotter your car the harder the air conditioner works. It is not a good idea to use the AC to its fullest capacity. When the car is parked in the shade, consider keeping the AC idle.
  • When your car is running at a high speed, do not run the AC to its fullest capacity. Keep the windows up. And when the speed is below 40 miles per hour, keep the windows down. Your car will not use extra gas if you run the vent.
  • The size of the car is another important factor to consider. The efficiency of the AC to some extent depends on the engine size and the body of the car. The AC can cool your car more quickly if the car is not huge. To save gas, you can consider getting a smaller car.

The bottom line

How much gas does AC use? We have seen that it depends on multiple factors. Whether you roll the windows down or use the AC, you can not cool your car without using gas. When you are driving your car, do what is comfortable for you. Yes, your car AC uses gas, but that is not a good reason to leave it unused. During the summer, no matter how much gas your AC consumes, you will use the AC.

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