Quote Originally Posted by Mike Henderson View Post
I suppose, technically, that all you need to generate is the amount of energy that the car is using cruising along the highway, plus a bit to put some in the battery for when you have to hill climb. Cruising along a flat road doesn't take a lot of HP - Google says between 10 and 20 HP. Ignoring efficiency, 15 HP is 11.25 kW. So the generator would have to be at least 15 kW and 20 kW would be better.

A 20 kW generator is not a small (or cheap) generator. It would take a lot of the truck bed.
Kinda what I expected. A quick look at the Harbor Freight catalog shows ~200lbs for a 10KW "portable" generator, which makes it a 2+ person job (or an engine hoist) to get it in or out of the bed.