Does using an automobile’s air conditioner while driving increase fuel consumption?

Question

Does using an automobile’s air conditioner while driving increase fuel consumption? What about driving with the lights on? What about playing the car radio when parked with the engine off? Explain in terms of the conservation of energy.

Answer 1

theoretically -- yes

yet fuel consumption is much more affected by other factors like soft tires (that are inflated less than specified pressure), any present of strong wind or anything that increases the drag -- for example, when I travel long distances with the bicycle mounted on the back of the car, the drag and fuel consumption increases noticeably.

Answer 2

Everything you mentioned results in more gasoline being used than if you didn't do it. The air conditioner uses about 0.5 HP, which doesn't seem like much, but a typical car cruising at 60 mph uses less than 20 hp to do so. All of a sudden, half a hp is 2.5%. The other items have smaller penalties, but EVERYTHING that uses ANY kind of energy in the car derives it from the fuel. Yes, that includes driving with the windows down (more drag) and running the radio with the engine stopped (the energy lost by the battery is replenished later by the alternator, which is driven by...the engine)

Thes are the physical facts in the matter.

Answer 3

Anything that puts a load on the engine uses more fuel .
The a/c uses approximately 6-12horsepower depending upon what make and model. The automakers have used wind tunnel tests on newer vehicles and designed them to use less fuel at speed with the windows closed and a/c on then with the windows open.
The lights and radio would only pull approximately 1/2-3 hp under full power,not enough to worry about.
The radio without the engine running is using battery power only,as long as the battery is charged enough to start the engine there shouldn't be a problem , the alternator will use some power to recharge the battery and then taper off usually within a few minutes. The engine would use more fuel energy then what the radio would use per minute .

Answer 4

Airconditioning causes a car to use more gas.. A compressor is used to compress the coolant and when it expands this is where the cooling comes from. The energy to compress the gas (coolant) comes from the engine.
At highway speeds the additional drag created by having the windows down will use as much gas as the a/c.
Electricity is created by the alternator this charges the battery that is drained to some degree every time the engine is started. The engine has to supply power to turn the alternator. This is not free, the energy has to come from somewhere and it comes from the use of more gas. The radio and lights are small users of electricity.
Listen to the engine when a car is jump started, the car with the engine running will slow under the additional load of producing enough power to start the other automobile.

Answer 5

What is conservation of energy? It states energy can neither be created nor destroyed. A car engine -through combustion - coverts chemical energy in unburned fuel into the mechanical energy of the rotating driveshaft. This rotating energy is then used to:
a) Rotate the car wheels and move the car forward
b) Charge the car battery through the alternator
c) Run the A/C compressor
e) Open and close engine valves via the camshaft

The alternator, compressor, and camshaft are all connected to the drivetrain with belts. When your AC is off, the compressor cog rotates freely, and the engine also draws less energy. When you turn your AC on, it draws some of the mechanical energy, and the engine has to work harder.

All the electronics (lights, radio) run on the car battery, but that energy came from burning fuel. The A/C compressor is also powered by the same fuel.

Everything your car does requires energy and the source of that energy is fuel.

Answer 6

The physical law of conservation of energy says essentially that you cannot get more work out of a system than you put into it. The engine burns gas and that causes levers and gears to go round - the more levers and gears you cause to go round, the more work is done, so the more gas you use.

But your car radio runs off the electricity produced by the battery, or off the electricity produced by the alternator, which runs anyway whether the radio or lights are on. So these don't use up gas. They use up the electricity in the battery when the car is off, or use the electricity produced anyway when the car is on.

As for the air conditioner, you do in fact use more gas driving with it on - some cars are more efficient than others about this, but the air conditioner adds to the work the car does, so the car uses up more gas.

Answer 7

The air conditioner does consume more fuel and extra energy from the engine. You might notice the car runs slower than usual when the AC is on. I doubt AC works to cool a car unless the car is running.

The lights draw energy from the battery as does the radio. As long as the car is running the battery will recharge itself, though if the car is not running both will drain the battery's power. Usually not enough to prevent the car from starting, but if the battery is old and not charging well it can.

Answer 8

A car does use more gas when running an air conditioner because the air conditioner runs off of the engine. However, the lights and the car radio do not effect gas consumption because they run off of the car battery.

Answer 9

The air conditioner compressor is directly driven off the engine by a belt - it simply puts an extra load on the engine which requires more fuel. Your lights, radio and other electrical devices draw a much lower amount of energy from the engine.

Answer 10

The simple answer to your question is YES. Anytime you extract power from an engine or motor, it requires more fuel to operate that engine or motor. It's simply a matter of, "you can't get something for nothing". In actual application in an automobile there is a point where operating the air conditioning is more efficient than riding with the windows down. It depends on the automobile, that is, how aerodynamically efficient the car actually is. I have read several article in various magazines that indicate the typical speed where this occurs is between 35 and 40 miles per hour. That means that a point between 35 and 40 miles per hour the reduction in wind drag gained by rolling up the windows offsets the increase in fuel consumption caused by extracting the additional power to operate the air conditioning. If you watch any of the police documentary type shows where the camera crews film actual pursuits conducted by police you will note they typically attain speeds approaching 100 MPH. You will seldom see their patrol cars with the windows down. It is my understanding that most police departments have a "windows up" pursuit policy. The policy is there to eliminate any possibility of something blowing through an open window and distracting the driver. In addition, it makes the car much more "slippery" as it moves through the air. I tried to answer this as completely as I could. I hope it helps. The additional information is to answer the question you didn't ask, but seemed to be screaming for an answer.

Answer 11

Using the air conditioner does not increase fuel consumption if you plan on compensating with leaving the windows open. The wind entering your vehicle will cause drag which will force your car to work harder which will in turn consume more fuel.

Your car radio runs off your battery, not your gas tank.