8,192 posts, read 23,724,630 times 3,040 posts, read 8,930,309 times Originally Posted by Racelady88 115V x 15A = 1725 Watts Due to inrush (starting) current, you will want to go at least 25% bigger. I would recommend one even larger than that, probably something around 3000 Watts, though you could probably get by with 2500 Watts. These are for peak load ratings. Sustained load ratings should be around 2000 Watts. Don't forget that with a window type A/C unit, you will need to mount the shell of the unit outside the van for proper venting of the hot exhaust air. This will most likely need to be out the rear of the vehicle so it doesn't protrude beyond the sides of the vehicle into an adjacent lane. Also keep in mind that if the inverter is being run off the starting battery that it wouldn't take long for the battery to drain to the point where the vehicle won't start. You will most likely want to be sure that there is a separate battery for the inverter, and that it is isolated from the starting battery so the ability to start the vehicle isn't compromised.

You'll also want to be sure that the vehicle's charging system is adequate. Also remember that in order to keep the batteries charged in the vehicle, the engine will need to be run long enough to recharge them. 4,515 posts, read 17,060,880 times Originally Posted by jdavid93225This is what I needed to know. I have a brand new deep cycle RV/Marine battery to push the inverter. The unit is going to take the place of one of the rear windows. He is going to be so excited to have A/C. 3,020 posts, read 20,105,444 times 3,460 posts, read 3,731,105 times 1800 Watts at 12 volts would be 150 Amp draw on the alternator/battery....ouch I'd look at one of the RV units runner mentioned. They should already be set up to run on 12 volts. A ROOM AIR CONDITIONER WILL ONLY WORK FOR ABOUT 20 MINUTES OR LESS ON BATTERY POWER FROM TWO BATTERIES. A single battery might not even provide the amperage to start the AC after the first couple uses. Boy times have really changed...