Been using a Honda 2000 watt gas generator with a built-in invertor for 2 years now. Bought it for 1000 bucks (In Delaware, no state tax!) It burns around 6-10 hours on a gallon of gas. I built a heavy duty vented wood box with a swing-up door on the front of it, and bolted it to my van's rear door, and used heavy metal L-brackets. In the summer, I run a 6000 BTU window AC, mounted in the window of the van's side door. Does well up to around 100 degrees. Over 100, it only cools down to around 80. In the winter, I use a 750-1500 watt electric heater. So far, I haven't needed the 1500 watt setting. I imagine I will when it drops below 20 degrees. There's a little more maintenance involved with the Honda; pouring gas in it, frequent oil changes, pull starting, spark plug change every 2 months or so, etc... , but since we sit every other day in these vans, it makes for some time-killing chores. At least, that's what I tell myself on a cold windy December night at 3 AM in Wisconsin pouring a gas can into the generator...