Why does automobile air-conditioning waste gasoline?

Question

To me it makes sense that the use of air conditioning to keep cool in an automobile would waste water and Freon. How does gasoline interact with auto air conditioning?

Answer 1

The more load you put on your engine, the harder it needs to work to run. There are many devices that run off of the engine; the power steering pump, the water pump, the alternator, and the AC compressor are the most typical of these devices.

Let's say you have an engine with no devices attached, running at idle. The engine needs to make only enough power to keep itself turning, and so burns a certain amount of air and gasoline.

Now, add on the water pump and other accessories. Some of these accessories make the engine work harder constantly (water pump), while others make the engine work harder when they're in use (power steering pump, very little load when going straight or turning at speed, but significant load when turning while stopped or at low speed.) As this load increases, the engine needs to put out more power to keep turning at the same speed -- and so it needs more air and gasoline.

The AC Compressor is a unique device (drive accessory, is the official term) in that it puts little to no load on the engine when it is turned off, but when it is turned on and the compressor is engaged, it puts a significant load on the engine -- so much so, that if your car is an underpowered 4-cylinder, you'll probably feel the engine slow down momentarily when you first turn it on at idle. Within moments, the engine starts gulping additional air and gasoline, and it returns to the proper speed.

The reason people commonly say AC is "wasteful" is because they look only at the fuel consumption when making that judgement. It is true that having the AC turned on makes the engine work harder (and so consume more fuel) than the engine does when the AC is turned off; however, there are other factors that can partially or completely offset this consumption:

1. Driving at highway speeds with the windows up and the AC on uses more fuel to overcome the AC compressor load, but less fuel to overcome aerodynamic drag, compared to driving at highway speeds with the windows down and the AC off;

2. If it's a brutally hot day, the additional expense of the extra fuel you burn will likely be more than offset by (a) the comfort that you derive from using the AC, and (b) the huge bottle of Gatorade you need to buy from the 7-11 every hour to keep from dehyrating.

One last thing: actually, the water generated by the AC system is water that collects on, then runs off of, the AC condensor...and the freon is contained in a "sealed" system, where it repeatedly compresses and expands, but the overall level does not change (unless there's a leak). Consequently, using the AC does indeed use more fuel than not using the AC, but there is no waste of either water or freon involved.

Answer 2

The A/C does not waste water or freon. The a/c has nothing to do with water. The a/c is a closed system that cycles freon. However, in order to get rid of excess heat, the refrigerant must be compressed with a compressor. This takes power to do so, and that power comes from the engine. So to travel the same speed when you don't have the a/c engaged, takes more power or more fuel. And it does not make the engine less efficient. The engine efficiency has nothing to do what it operates. It just means you are using less of the engine's power to move the car. It has nothing to do with the batter, like some people are saying. The compressor is generated by mechanical power from the engine, not electricity. And the only reason those studies show you use less fuel than just having the windows down, is because those tests were done at high speeds. The aerodynamics of the car are worse with the windows down. Therefore, the loss of power due to the a/c is less then the loss of power because of high drag, but only at high rates of speed. At low speeds, the aerodynamics have little effect on vehicle drag, and the a/c will be more dominant.

Answer 3

It doesnt waste water or freon.
The A/C unit compresses cool freon gass into hot high pressure freon gas which then passes through tubing until it cools and condenses into liquid freon.
Then it passes through a valve and expands and evaporates into COLD freon gas. This cold gas passes through tubing where enviromental air gets blown over it. The cold gas in the tube absorbs the heat in the air and moisture in the air condenses on the tube.
To run the compressor/condenser, the ac unit is attached via a belt to the engine. Running the a/c robs the engine of power, thereby using more gasolin to go the same distance.

Answer 4

the AC doesnt waste freon, if the system is sealed properly, nor water-again, if the system is properly sealed. The AC motor, which runs the gas compression and fans, is driven by a belt connected to the engine- This AC motor actually takes a fair amount of energy to run-all of it supplied by the turning of the AC belt by the engine itself- thus, the engine has to burn gasoline in order to turn the AC belt, which in turn powers the AC motor compressor itself.
An interesting fact from my days as a streetrod racer- IN order to keep your engine cooler, run the heat- The heat used to warm your car's interior comes from the engine itself- thus if you run the heater, it pulls some of the heat from the engine- So, if you are running your car hot, or putting it through high RPMs, its a good idea to run the heater full blast in order to help keep the engine cool.

Answer 5

Depending on your car accesories, and the way its built.
Air Conditioning is attached to the car engine circulating coolant and air. Tapping the power of the engine.
Most cars use only 20-30% of the energy-power of the engine to the car wheels, the rest is waste. Why? Lack of a better mechanical engineer, and cost of research.

Answer 6

in traffic let windows down when driving run ac reduces drag saves gas there has been many tests that prove this

Answer 7

motor drives the ac comprise and power the ac fan that will make it use eingen hourse power that will make it use more gas

Answer 8

pulls more power, makes car work harder.

Answer 9

in traffic

Answer 10

A black hole