Our gasoline Espar seems to use about a gallon per 8 hours versus the optimistic figures that we were sold on. In addition, our gasoline Espar cost almost $2,500 installed versus $300 for a Chinese generator and space heater. The fuel use may be a bit higher but I have to wonder if it will ever really pay off???
A lot of that depends on how well your van is insulated. If it's not insulated very well, it'll run on the higher mode more of the time, resulting in more burned fuel. The airflow inside the van can also make a big difference, as you want the airflow to evenly distribute the heat rather than having hot and cold spots, which will result in having to work harder to heat the same space.
$2500 for an Espar to be installed sounds a little high. Are you sure that costs doesn't include an aux battery, cables and an isolator?
If you do a thorough cost analysis, you'll find, not surprisingly, that an Espar heater will be far more cost effective than idling the vehicle's engine. The Espar will pay for itself the first winter in most cases. It will take longer to recoup the costs when comparing it to a cheap generator and a space heater, but you also need to factor in the regular maintenance of having to change the oil every couple of weeks in a generator, rain, snow or shine, and having to deal with either filling the generator's gas tank in the middle of the night, or lugging around an external tank with more fuel capacity. A $300 generator isn't likely one to last very long, either, so replacement costs should be figured into the analysis. Some have been known to last as long as three years, others didn't even make it though the first winter.
There are pros and cons to whatever method used to heat the truck. But a good cost analysis will help with the decisions.
My first winter out here I idled, and then went with a generator and a space heater. The next winter I had an Espar, and I've had one every winter ever since.