Webasto or Espar?

The combo coolant bunk heater would require more batteries, 6 maybe. Buddy of mine needs to start his after 7 or 8 hours if it is cold. I have two separate webasto units, timer set engine coolant unit and the 2000 st for the bunk and I just run 4 batteries(2012 prostar). I have used this setup north of 60 when nightime temps got down to -25f on one of the nights with good success and the small 2000 bunk heater was not taxed too hard even with that temp. As for install, it seems easy, though I cheated and had my truck speced with them. Maintenance is less if you run the units monthly when in off season, and even swapping parts out is simple and parts are easy to find.