Question: How long can my car be parked with the air conditioner on and the engine running without causing damage?
Answer:
While there is no definitive limit, part of this answer depends on how concerned you are with wear and tear on your engine or the fuel consumption of your vehicle. Some will recommend not idling for more than 10-15 minutes to avoid unnecessary wear and use of fuel, but if you’re not concerned with that, you could feasibly run it for longer. That said, it’s advisable to turn off the engine for lengthy periods and use other methods to stay cool whenever possible.
Is it safe to sit in a running car with the air conditioner on?
If you’re sitting in traffic or just waiting outside in a parking lot to pick someone up, sitting in your car with the AC on is perfectly safe. The key consideration here is that you’re outside. Idling in an enclosed space, such as a garage, can lead to a build up of dangerous and potentially lethal carbon monoxide.
Safety aside, even if you’re outside with the AC off, it’s still best to shut off your car if you sit idle for more than a few minutes.
But isn’t frequent restarting harder on your car than idling?
No—idling is actually harder on your engine in the long run. While frequent restarting only costs an average of about $10 per year in wear and tear on your car, idling leaves fuel residues that can damage your engine and lead to much higher maintenance and repair costs over time.
Factors to consider when idling with the AC on
In many cases, the determining factor for whether you should run your AC while your car is parked has less to do with the AC than with idling in general. With that in mind, here are some key things to think about when deciding whether and/or how long to leave your car running while parked:
Overheating and temperature maintenance
Your car’s cooling system has to work harder to keep the engine and air conditioner functioning correctly while idling. Overheating can become an issue, particularly in hot weather or if the cooling system is not in optimal condition.
In addition, your air conditioning system might not be as efficient at cooling when the car is stationary compared to when it’s moving depending on external temperatures and the system’s condition.
Engine wear and tear
Prolonged idling can lead to increased wear and tear on the engine, especially if it becomes a regular habit. Components in your engine such as spark plugs, belts, and the cooling system may experience more stress.
Battery health
While the engine runs, the alternator charges the battery. However, if the air conditioning system drains more power than the alternator can provide, it might affect the battery’s charge, especially in older vehicles.
Fuel consumption
If you choose to leave your car idling with the AC on, not only are you wasting fuel, but you also run the risk of running out of gas. The rate of consumption depends on the car’s engine size, make, and model, but a car idling—even with the air conditioner off—typically uses about a half gallon of fuel per hour.
Environmental impact
Idling for extended periods contributes to air pollution and greenhouse gas emissions. Many places have regulations against unnecessary idling to help curb environmental impact.
Sarah Gray is an insurance writer with nearly a decade of experience in publishing and writing. Sarah specializes in writing articles that educate car owners and buyers on the full scope of car ownership—from shopping for and buying a new car to scrapping one that’s breathed its last and everything in between. Sarah has authored over 1,500 articles for Jerry on topics ranging from first-time buyer programs to how to get a salvage title for a totaled car. Prior to joining Jerry, Sarah was a full-time professor of English literature and composition with multiple academic writing publications.
Everett Cook is an award-winning journalist and editor with more than 10 years of experience across a variety of industries. In editing for Jerry, Everett’s mission is to help readers have a better understanding of the costs of owning or leasing a car and to better understand their vehicle in terms of insurance and repairs. Prior to joining Jerry, Everett was an editor for Axios. His previous work has been featured in The New York Times, The Los Angeles Times, The San Francisco Chronicle, The Atlantic, Atlantic Re:think, The Boston Globe, USA Today, and others. He’s also been a freelance writer and editor with experience in SEO, audience building, and long-term content roadmaps. Everett is a proud graduate of the University of Michigan.
