how long can you keep car running with ac

[MacCora]

You can typically keep a car running with the AC on for several hours, but the exact duration depends primarily on your vehicle's fuel capacity and its rate of consumption. A modern car idling with the air conditioning running will consume between 0.2 and 0.8 gallons of fuel per hour. This means with a full tank, you could theoretically idle for over 24 hours, but practical and safety considerations make this ill-advised.

The biggest factor is your engine's size and efficiency. A large V8 engine will burn significantly more fuel at idle than a compact 4-cylinder engine. The electrical load from the AC compressor, which is belt-driven by the engine, creates the extra demand. While idling for short periods (like 30-60 minutes) is generally safe for a well-maintained vehicle, extended idling can lead to other issues.

Potential Risks of Prolonged Idling:

• Engine Overheating: The primary cooling system (fan, radiator) is designed for airflow while moving. During extended idling, especially on hot days, the lack of airflow can cause the engine to overheat.
• Carbon Monoxide Poisoning: This is the most critical danger. Never idle a car in an enclosed space like a garage. Even outdoors, exhaust fumes can seep into the cabin if there's a leak or the car is positioned near a building with the wind blowing the wrong way.
• Component Wear: Idling causes "low-speed" engine wear on components and leads to faster degradation of engine oil.

For electric vehicles (EVs), the calculation is different. The AC runs on the high-voltage battery. Depending on the outside temperature and the battery's size, an EV could run its AC for 8 to 24 hours on a full charge before the battery is depleted, making it much more suitable for scenarios like camping.

Vehicle Type	Estimated Idle Time with AC (Full Tank/Charge)	Key Limiting Factor
Compact Sedan (4-cylinder)	20 - 30+ hours	Fuel Capacity
Full-Size SUV (V8)	10 - 20 hours	Fuel Consumption Rate
Hybrid Vehicle	24 - 40+ hours	Fuel Capacity (engine cycles on/off)
Electric Vehicle (EV)	8 - 24 hours	Battery State of Charge
Diesel Truck	30 - 50+ hours	Large Fuel Tank & Efficient Idle

[MadelynAnn]

Honestly, I’ve done this waiting for my kids at practice. In my SUV, I’ve left it running with the AC on for a solid two hours and it used just under a quarter tank. The key is to make sure you're parked in a wide-open area so exhaust doesn't build up. It’s fine for a long wait, but I wouldn't make a habit of it every day—it's not great for the engine and gets expensive.

[LeIris]

The safe operational limit is less about mechanics and more about safety. The primary risk is carbon monoxide. Always park outdoors, far from windows or air intakes. Ensure your exhaust system is leak-free. Mechanically, a healthy car can idle for many hours, but it's an inefficient way to cool down. For regular, long-duration needs, like a worksite, consider a dedicated portable power source for climate control instead of idling your vehicle.

[OAugust]

We use our truck for tailgating all season. I’ve monitored this closely. Our V8 will go through about half a gallon per hour with the AC blasting. We can easily run it for 6-8 hours over a game day without worrying about the fuel gauge. The engine temp gauge never moves because we’re always parked in an open lot. Just listen to your vehicle—if it starts sounding strained or the temp creeps up, shut it off and let it rest.

[CollinDella]

From an efficiency standpoint, idling with the AC is wasteful. An idling engine gets zero miles per gallon. If you're planning to be stationary for more than a minute or two, it's often more fuel-efficient to turn the engine off and restart it later. Modern starters are designed for frequent use. The best practice is to use the AC while driving, and limit idling to short periods. For longer stops, seek shade or use a solar-powered fan.