BIGNASTY, the Espar is really nice, and is the best thing you can add do for your Cummins I had one in my 02 when we lived in Anchorage. It is really nice to program it to come on approx 1 hour before you get out of work. At -30 it will melt ice and snow off the hood, roof, and windshield before you get in it. I had a controller that you could program to blow warm air through the defroster. This was set on low speed as to not draw too many watts. You could program, if I'm not mistaken, for 2-3 events per day, and up to one or two weeks out in advance. When I started the truck I had instant heat and the engine cranked and fired as though it was 60 degrees outside. Short tripping a diesel in cold weather is the single worst thing you can do to that engine. With the Espar it takes the worry out of your mind.
Good luck in Montana!!! Beautiful State in that NW.