The freezing point of propane is -187ºC. so it won't freeze up in the tank, Propane still can vaporize down to -44 F
With out 2-stage reducing valves, it lessens the pressure drop. I don't like the idea of using ANYTHING electric or any type of heat pon a Propane tank, some do, but not me..no sir...
Now, you can get contanamited Propane from suppliers with moisture in it, but that would be very rare..
It happens when there is a big draw on the tanks, less with the 2-stage regulators, like I stated abobe.
Info from the Internet:
Q. Why does a propane tank freeze up or sweat?
A. When the vapor in a tank/cylinder is being drawn down quickly, it lowers the pressure in the tank. The liquid reacts to the low pressure by boiling and creating a -44 degrees below zero temperature inside the tank, freezing the outside moisture on the tank. By turning the gas off and eliminating the draw on the tank, the pressure will recover.
Hybrid Mode
