Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. How Much Power Does the AC Draw From the Engine?

How Much Power Does the AC Draw From the Engine?

ac engine

Most cars these days come with air conditioning as a standard feature – gone are the days when it was an expensive extra (for most of us, anyway). The HVAC system is an important accessory, and helps you stay cool in the car when it gets hot outside. However, the AC is powered by your engine – the serpentine belt that runs your alternator, water pump, power steering pump and other accessories also turns the pulley for the AC compressor/clutch.

How the air conditioning system affects the engine

Because the system is powered by your engine, it pulls energy from it during operation, which can have an effect on engine performance. You’ve likely noticed your car’s engine RPMs increasing at idle when the compressor kicks on. It does this to offset the power drawn by the air conditioning system.

As to the question of how much power it draws, there’s no one answer, as it depends on the make and model, the engine, the condition of the engine and the air conditioning system and much more. It also depends on your acceleration and the year (most cars manufactured after 2000 have a relay that shuts off air conditioning at WOT (wide open throttle)) to ensure ample power for the engine under hard acceleration.

You’ll also find that the power drawn from the engine has a more noticeable impact with smaller engines. If you drive a subcompact with a small four-cylinder engine, your engine will be much more affected during AC operation than a big block V8 engine, even if the amount of power drawn by the air conditioner is identical between the two cars.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


More related articles

P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...

Related questions

Q: Water pump leaking and no pressure in the engine head

You did not mention if the engine was having any running issues other than the two lights coming on. Without knowing the codes that were stored and the actual problems causing the cylinder head to have no compression or coolant...

Q: How do I set dual zone temperatures?

When the dual zone temperature setting is turned on, then the driver side and passenger side temperatures can be adjusted separately. To turn this feature on, press the Dual button. Press the button again to turn the system off and...

Q: Stalling dying misfires

These issues may be related. The battery is basically just an electronic storage device which must be charged regularly by the alternator. A good battery that doesn't stay charged points to a failing alternator. A bad alternator can also cause...