for those that warm there smoke house with propane what kind of run time do you get on
a 20lb tank @ 170deg?
Gonna depend on too many factors to give a one-size-fits-all answer. Eg: Smoker size, insulation, outside temp, etc.
But, as an example, I use a modified UDS with an external smoke generator and a 15000 btu burner (about 6" dia) well insulated. As a lb of propane contains aprox 20000 btu a 20 lb tank = 400000 btu
If I am running the burner full throttle it will last about 30 hours. As a practical matter for hot smoking I usually only need about 1/4 throttle and the bottle will last about 10 average runs before it's empty. Always keep a spare as you sure don't want to loose heat in the middle of a run.
Hope this helps some.