Espar heater. Live comfortably. Live cost effectively.
Recently in -15F degree weather I was warm and toasty lounging in the van wearing less than a shirt and pants. No wasted money in fuel and engine wear to idling.
Depending on the Espar model, it'll cost between $1500 and $2000, which is also the same amount that you'll spend wasting fuel to idle over one winter. And that's if you idle minimally. If you idle most or all of the time, the Espar pays for itself in a couple of months. Next winter it's all money in your pocket.
Your mileage may vary, but if you idle 8 hours during the week, then idle all weekend, you're looking at 100 hours a week, which is about 100 gallons of fuel a week. Multiply that by the cost of fuel, then divide that into the $1500 or $2000 cost of an Espar, and that's how fast the Espar pays for itself (not including cost of engine wear).
It's a no brainer.