That's my deal, I will run a timer to avoid wasting KWH. If an hour does it I am typically up an hour before departure, so just switching it on will do it for me. I think the truck is going to be a 2 hour minimum, with a 5 gallon coolant capacity and 950 pounds of engine iron.
1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears