I learned that you can determine the tare weight of your household propane tank, assiduously weight it twice weekly, the most certain way to know you're low on gas is to unexpectedly run out of gas.
(Our range and water heater operate off a 30kg propane tank, exchanged by truck whenever we need one)
(Our range and water heater operate off a 30kg propane tank, exchanged by truck whenever we need one)