While I grew up in SD county, I now am in a slightly cooler area. In normal cold spells there is minimal need to plug in something gasoline powered. I will plug my Diesel in if the temp is going to be around zero (and that's only for an overnight park). Batteries and oil are usually what keeps a gas powered rig from starting. In extreme cold (way up North) it would help, and it makes for a quicker warm up. My diesel is putting out good heat within a couple blocks of the house.
One cold spell, I couldn't get a gas powered 79 Bronco to start, I lit a can of Sterno and placed it on the ground below the engine bay. This was a lifted truck and I didn't expect much. About an hour later the truck spun over and started like it was summer time. The simple heat was enough to "thin" the oil and warm the battery.
In-door parking (out of the wind) has a big influence on morning starts as well.