I have been using mine for the 4th winter now..it cost about $150 and i don't use the 1 lb bottles, i have 2 16 lb tanks in the truck..depending on how high you run it and how long, the run time will very...I have run it continously on the medium setting for 3 days and it didn't run out, and it was nice and toasty in the van in 18* degree outside temps...on high, it will run you out of the van...
I have no idea of the btu/watts conversion, as it makes no difference to me whatsoever..its cheap to run and the cost is low...
Yes using propane is fine, but you have to be safe..while the unit has a "low oxygen shutoff built into it, i use a carbon monoxide detector, open both ft windows about 1.5 inches and open the roof vent...even with those openings and the wind blowing outside, the van is still as warm as i want it to be in any situation...now that being said, my van is insulated as good as it needs to be to contain the heat....