I have the Big Buddy model which has two heating elements and a fan. It takes two small propane bottles. Using both elements it will get the entire front area of my coach comfortably warm within minutes, it seems. But using both elements is too much because the propane will only last about 3 hours and the coach gets way too warm, so one element is really enough for the front area. The heat does not reach the back bedroom as well. I keep the driver and passenger windows open a crack for ventilation and I have two CO detectors in the coach. We also use it for ice fishing and usually wind up just wearing t-shirts while we sit in the shelter. I'm very happy with it.