When it’s hot and opening the windows isn’t enough to cool you off, turning the AC on offers quick relief.
But does AC use gas while it’s running, decreasing your fuel mileage?
With the price of gas approaching an all-time high, this is a question you need to answer before hitting the road.
We’ve previously discussed how to save money on gas, but now we’re getting granular and addressing one of the biggest topics that drivers should know.
Table Of Contents
Does AC Use Gas?
Yes, running the air conditioner in your gas-powered car uses gas.
Typically, the engine’s power ultimately drives the air conditioning system through electrical power generated by pumps and the alternator.
Which Uses More Gas: AC or Heat?
The heating system in your car uses the warmth of your running engine to create the hot air that eventually blows out of the vents on your dashboard and elsewhere.
It’s actually a bit more complicated than that, but the bottom line is that since the engine is already hot, it doesn’t take too much extra work from the engine to generate heat.
But, running the heater does require powering fans to circulate the air.
Those fans get their energy from the car, and that does mean using more gas than you would without the heater running at all.
Typically, running the heat uses less gas than running the AC system.
How Much Gas Does AC Use?
Air conditioning will drop your miles per gallon only slightly when it doesn’t have to work too hard.
When it’s very hot out, and the system is really cranking, it can cost you a few miles per gallon.
For example, in a recent study from Consumer Reports, they found that running the AC will cost you between one and four miles per gallon of gasoline.
Much of the variation in fuel consumption corresponds with changing ambient air temperatures.
The hotter it is, the harder the system works, and the more gas you burn.
How Does AC in Your Car Work?
AC in a car works pretty much like the air conditioner in your home.
At the heart of the system is a highly pressurized gas called refrigerant.
A compressor forces the refrigerant into a liquid state, so it can flow through the system and into a condenser.
The refrigerant gas is usually freon, which is federally regulated.
Air conditioner repair is a specialized service, whether it’s for your cair air conditioner or your central AC or HVAC system at home.
Only qualified technicians can recharge your car’s air conditioning system.
So if you think your AC is blowing warm air and that it needs more freon, you’ll need to take it to a shop where they have trained techs to service the HVAC system.
You’ll also need a qualified tech for:
- Any AC repair
- Checking the refrigerant level
- Servicing the AC compressor
- Adding freon
- Problems with the condenser coil
- Any air conditioning repair that requires opening the pressure system
The condenser coil removes the heat from the flowing refrigerant and passes it through an expansion valve that allows the refrigerant to return to a gaseous state.
The refrigerant then collects on a receiver, called the accumulator, which removes moisture from the gas, and transfers it to the evaporator.
Finally, the evaporator coil comes into contact with warm, ambient air.
The hot air passing through the evaporator core passes over the cold refrigerant, transferring its heat.
Finally, the fan blows the now-dried and cool air back into the cabin.
That’s how an air conditioner system keeps the climate in the car’s cabin comfortable and the indoor air quality high.
It also helps keep the windshield free of moisture which is important for visibility and safety regardless of gas mileage.
How Does AC in an Electric Car Work?
An electric car doesn’t have an internal-combustion engine to power the air conditioning system.
All the energy comes from the battery.
So, just as the use of the AC system in a gas-powered car affects mileage, you’ll experience reduced mileage in an electric car too.
But, the system works in essentially the same manner in modern electric vehicles, like Teslas.
Some new and innovative systems use a desiccant to remove moisture from the air before it passes through a highly efficient and smaller AC system.
Electric vehicles are, in many ways, the new frontier of passenger car construction.
As such, they are spurring a whole new attitude in the design process and yielding increased efficiency.
Automotive engineers are constantly trying to improve the design of the AC unit.
So, the AC system in an electric car tends to be very efficient, as it’s not bound by traditional design limitations.
You don’t have to worry about increased gas consumption, but you should still consider limiting the use of your car’s air conditioner to save energy.
Electric cars also need fewer trips to the shop for air conditioner repair, as the air conditioning unit is typically quite reliable on new vehicles.
Can Using Car AC Be Fuel Efficient?
Using the AC is sometimes more fuel-efficient than not running the system and opening the windows.
That’s because when you open your windows, it changes the airflow over your car, letting air inside the cabin and creating drag.
That aerodynamic inefficiency will lower your fuel economy.
So, when you’re traveling at highway speed, say sixty miles per hour, or faster, it is more fuel-efficient to use your AC to cool off, as opposed to opening the windows and creating drag.
Related: How to get free gas
Is It Worth It to Use the AC?
For people who are sensitive to heat or have health conditions that make it harder to breathe in high humidity, running the AC is always worth it.
But, there are some tradeoffs to consider.
Pros of Using the AC
- Keeps the temperature from becoming uncomfortably hot in the cabin
- Prevents moisture from building up inside of the car when the fresh air is humid
- Dries the air to limit condensation on the inside of the window
- Preserves aerodynamics and limits air resistance of the car
Cons of Using the AC
- Can lead to condensation on the outside of the windows
- Using the AC may negatively affect fuel mileage
- Robs your car of some performance to provide cooled air
So, Is It Worth It to Run the AC?
In many cases, it is worth it to run the AC.
It’s often good for you, your car, and your passengers.
On the flip side of that coin, cranking the air conditioner to the max fan and cooling settings when it’s not necessary, or using the AC when your car is idling, will both make it less and less worth it.
But, there are situations where it’s not worth it to run the air conditioner.
For instance, if you’re traveling slowly on a day when it’s quite warm, it may be advisable to open your windows instead.
You won’t experience a major loss in fuel economy due to the aerodynamic drag of your open windows because you’re not going fast enough.
Plus, since it’s very warm, your AC will have to work very hard.
So, enjoy the breeze with the windows down when you’re rolling slowly on a very warm day.
Then, when you get up to highway speed, roll the windows up to retain your aerodynamic efficiency, and turn on the AC to keep comfortable.
Ways to Improve Your Fuel Efficiency
There are many tricks to improve your fuel efficiency that aren’t related to your air conditioner.
By taking advantage of these techniques, you can probably offset any decrease in mileage created by running the AC.
Here are some major fuel savers that can boost your gas mileage significantly.
1. Use AC at High Speeds
Whenever you’re at high speed, leave the windows closed.
Instead, utilize the air conditioner and maintain your aerodynamics.
2. Go Light on the Brakes
It’s good practice to only use the brakes when you need to slow down.
Some drivers tend to be nervous on the brake pedal, tapping it more often than necessary.
By looking out far over the hood and well down the road, you can anticipate changes in the traffic pattern and prepare for slowdowns and stops by letting off the gas.
Doing so preserves your momentum as much as possible, and going easy on the brakes improves your fuel economy.
3. Don’t Idle
Idling your car is a recipe for decreasing your fuel efficiency.
It consumes gas and accomplishes little.
Especially when taking a wide perspective and considering how your habit over the long term affects your fuel economy, you should avoid idling whenever possible.
Now you know the facts.
Running the AC does use up a bit of extra gas in a traditional car.
Doing so in an electric vehicle also requires extra energy, running down the battery a bit faster.
So, you can become more efficient by limiting your use of the air conditioner in general, and only using it when you’re at a higher speed.
Plus, you can improve your overall fuel economy by never idling and going easy on your brakes.