How long can car idle on a tank of gas?

With all the talk about the hurricanes and seeing that stores are out of generators, it got me wondering if you could just use your car with a power inverter. Of course a ton of batteries would be the optimal choice but most people don’t even have any or many. Even I have only about 50 Ah of SLA batteries lying around and half arent even charged. SO, say you use your car to power an inverter. So all the time it is just idling with the load of the alternator. I know it depends on the car and engine and size of gas tank but can anyone give me an idea of how long it would last. Or at least how much gas per time the car consumes while idling? Thanks.

This is by no means an educated guess, but I’d imagine that you’d be good for a bare minimum of four hours, especially if your car’s engine is still good. You’d probably have to juice the throttle now and then to keep the engine happy, but other than that I think you’d be alright.

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this really depends on a few things…1 how large in watts is your inverter. i say this because your amperage off of the alternator varies with engine rpm. so to get a higher RPM you will need to apply more gas thus shortening your run time.

so for a small inverter like 50 watts, it can probably run on just the idle but if you get a larger one like 1200 watts you will need to open the throttle up more to keep the power flowing.

I actually did this when we had a power outage for almost a day. I wasn’t sure what was going on so I needed a way to run the TV for awhile. I used a 150W power inverter I have and used my '97 Toyota Camry (4 cylinder) to run the inverter. I only used it for about 1 1/2 hours but I let the car just idle out in the driveway and ran an extension cord back into the house. I don’t know the wattage of the tv off hand but it was a 13" I have in the kitchen. As long as the engine is in good shape, the fluids aren’t low, and the front of the car isn’t obstructed (like having it nosed into a shrub or something else that would decrease airflow) no damage should be done to the car or engine.

As for how long I don’t have an exact answer but the gas gauge on my 4 cyl Camry didn’t even move. I would guess that the car would run almost a full day on a full tank (18 gallons). If I had to run it all day I would still shut it off every few hours to give it a rest.

P.S. Too bad that inverter couldn’t run the 'fridge. We had to throw most of the food away…after we had gone shopping the day before. :frowning: Of course the alternator couldn’t handle that kind of a draw either.


I’d say minimum would be 3-days on my Jeep. (Inline-6 4.0, 90 amp alt at 14 volts)

Think how much energy is needed for your vehicle to travel one mile - and on a tank of gas I can get about 300 miles.

I wouldn’t worry about it…(just don’t draw too much power…)

Probably for quite a long time, for the reasons pointed out above. Try this for some peripherally related information on inverters (from 12 V DC batteries).

But just as a public service announcement, avoid carbon monoxide poisioning, no matter how comfortable your car’s seats are. Don’t do something you won’t live to regret.

yesterday i tailgated the UCF football game and we were using my car stereo as a bom box. 800 watts (max) pulling for 6 hours with the car idling. I have a 3.3L V6 thats in great shape. Even in the hot central florida sun the temperature gague stayed right where it is supposed to be. I proabaly used 2 gallons of gas, if that much. My car has a 110amp alternator.

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Andrew - it isn’t a Intrepid is it? Or a Caravan?

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And about your 800 wats max - that is when It hits at max volume. I bet you where running at about 1/5 power and when it hit at about 1/2 to 3/4 power.

Even at that rate - you where still pushing 160 watts (and that’s a loud system - so I bet even less at ‘normal’ volume)

Close Guess with the Caravan. its a nissan quest. And i had the volume all the way up, we had to be loud enough so we could hear it over the crappy music playing a few spots away. All of my speakers are rated for much more watts than I’m capable of pushing through them.

Matt this is way off topic but i love that movie FEAR AND LOATHING IN LAS VEGAS, lol infact i am watching it right now with my roomate

Was that an add-on by you? Don’t most cars come with a 90amp alternator?

I thought the only cars that had higher one’s were VW’s for some reason or another.

I’d agree on most V-6’s but normally too you can get a better alternator just by asking. All of our chevys here (the 2.2 I-4 all the way up to the 6.0 V-8s have 2 alternators. Just one for the ‘base’ model and the heavier duty one for the ‘limited’ models.)

And standard on the Chrysler 5.2 is a 120 amp and on the 5.9 I think it’s 160 amp.