I have a propane tank.
They top off
There is evaporation
None of what you state seems out of the ordinary
Dangit. I can’t get away from these folks.
What sort of evaporation? If no vapor is being drawn nothing is leaving the tank.
I sold my propane co a few years ago to a major national co who are mostly all crooks and opportunists. They will play many pricing games.
Try to own your own tank. Only order after calling each co in your area.
don’t let tank run out
Re price of elect vs LPG - if memory serves me there are 3400 btu’s in 1 kilowatt and price per KW varies per your location. LpG has 91,000 BTU’s per gallon.
So about 27KW to equal 1 gallon of propane.
do that part of the math based on the prices in your area.
Usually tough for elect to be cheaper except certain regions of our country. Wholesale cost of propane goes
Up further away from oil refinery
Also look at the efficiency rating of each appliance ie water heater, furnace. Good lpg furnaces can be 95% each appliance has an info tag that if you’re willing to take the time you can zero in on good cost accounting.
The heat loss of yourhome will be the same whether you use gas or elect.
Most people live in areas served by natural gas - always much cheaper than eeither propane or elect