Does AC Use Gas or Electricity in a Car?

Are you wondering whether your car’s AC uses gas or electricity?

There are two power sources in your (gas-powered) car: gas and electricity; some people may be confused when driving their cars if they use gas or a battery.

This article clears this confusion up for you and gives some relevant information on the main components of a car AC.

The engine drives the AC compressor in cars by turning a wheel which subsequently turns a belt. So when your AC is on, the compressor slows down your engine by putting more pressure on the engine to generate the same power requiring more gas to keep the same speed. The more load on your electrical system, the more the alternator has to run, and the more it slows down. Your engine then requires more gas. 

How Car ACs and Electronics Work

The AC works with the following components:

  • *A compressor for compressing the refrigerant to make it fluid and flow through to the condenser.
    • **The compressor draws energy from the alternator
    • **The engine powers the alternator
  • A condenser removes heat from the refrigerant through the tubes and valves.
  • An accumulator to ensure the refrigerant is free from moisture and can carry it to the evaporator.
  • An expansion valve and orifice tubes restore the refrigerant to its gaseous state to transfer it to the accumulator.
  • An evaporator transfers heat to the refrigerant from the evaporator core (via the surroundings) to enable cold air to flow through the evaporator.

Why are so Many People Confused as to Gas or Electricity Use?

A common misconception is that since the alternator powers the AC, the car uses no gas from this process. It uses mostly electricity that is already there from running the engine. It’s clear how people can think that, but excess energy cannot be created from thin air; cars are extremely efficient and conserve any energy, so almost no excess that the alternator creates goes directly to the battery, and if the battery is full, the alternator works less.

Because of this, when you run your a/c, the alternator has to work slightly harder for the same amount of energy to be generated. The engine needs to work slightly harder for the alternator to work harder to power it. 

This “slight amount” is not very large. Below we’ll cover more detail on the exact values.

How Much Gas Does Running Your AC Consume?

Using your car’s AC will consume more gas because it runs on gas, making it less available for the car itself to run. How much it will consume depends on the quality of the AC and alternator and the car engine’s efficiency in consuming gas.

As a rough figure, you can expect it to consume around 5% more per mile, typically more than the car’s heating system would consume. In hot weather, it is used more and will consume more. It will also reduce the fuel economy, which will be especially noticeable during short trips.

Will Turning Off the Car AC Save You Gas?

Yes, it would, because the AC will not consume gas while it is turned off, but the saving will only be a little, perhaps not enough, to make a significant difference. If you aim to reduce fuel economy, it will be reduced if you drive with open car windows. You may notice the car will also run faster, more easily, with the AC turned off.

How Can I Save Gas when Using My Car’s AC?

When using your car’s AC, you can save gas by keeping the windows closed while the AC is in use and avoiding using it while traveling at a slow speed. To save gas, you should use it sparingly, but this defeats its purpose of keeping you cool when it is hot. It works more efficiently when you use it while driving fast.

Can a Car’s AC Work without Gas?

Yes, it can, but only for a short period depending on how much oil remains in the compressor. It cannot continue operating for long without a refrigerant.

If a Car’s Ac Uses Gas, How Do ACs Work in Electric Cars, and How Do They Compare?

Electric cars don’t have a gas-powered engine and alternator, so they cannot install a gas-powered AC. Their ACs rely on the car’s motor instead. If you can install either in a gas-powered car, a gas-powered one will be more efficient and powerful, and it will not drain your battery. The mileage of an electricity-powered car AC is typically affected more than a gas-powered car AC.

Electric Cars and Electricity-Based Car AC

To reiterate, a gas-powered car AC is operated by the alternator, powered by the engine, and consumes gas (also referred to as petrol).

Since there is no gas engine or alternator in an electric car, an electric-powered car AC is operated by the car’s motor instead and consumes electricity. It operates similarly to a refrigerator to provide cool air.

If you can install either type in a gas-powered car, it is generally better to opt for a gas-powered AC rather than an electricity-powered one. There are four main reasons why. Gas-powered car AC:

  • It is more efficient in cooling the car quicker and keeping it cool for longer.
  • It is more powerful, so it is more suitable for driving in hot weather and/or using it during long drives.
  • Does not rely heavily on the car’s engine. This means it can continue to work even while the engine is turned off.
  • Does not drain the battery, as with electricity-powered car ACs.

However, a gas-powered car AC can only be fitted if the car is compatible with it.

Wrapping Up

Although a gas-powered car’s AC can be either gas or electricity-powered, we pointed out that most have gas-powered car ACs installed because they are more efficient and powerful than electricity-based car ACs. Gas-powered car ACs draw energy from the alternator, which is powered by the engine. In contrast, electric-powered car ACs rely on the electric motor, which is their only option.

Take a look at some of our related articles below.

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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