Westys LP gas uses include cooking, refrigeration,
and in some examples space heating. The LHS
recycling shower uses it for water heating.
For those interested, this chart may be helpful:

LP Gas Gases and RV container sizes.
                              Propane    Butane
Pounds per gallon               4.24       4.81
Specific gravity of gas         1.53       2.00
Specific gravity of liquid      0.51       0.58
Cu. ft. gas per gallon liquid  36.38      31.20
Cu. ft. gas per pound           8.66       6.50
BTU per gallon                91,502    102,032
BTU per pound                 21,548     21,221
Boiling temperature @ 14.7
psi in degrees F                 -44         32
Vapor psi @   0 F                 31          0
Vapor psi @  70 F                127         17
Vapor psi @ 100 F                196         37
Vapor psi @ 105 F                210         41
Vapor Specific Gravity
(Define Air to = 1.00)          1.50       2.01
Ignition Temperature
in Air in Fahrenheit        920-1120   900-1000

Average Propane container capacity
assuming 20% vapor space
Nominal Size   Actual Capacity   Lb.   BTU's
2.5 gal. (10#)     2.5 gal.      11     237,028
5.0 gal. (20#)     4.8 gal.      20     430,960
7.5 gal. (30#)     7.2 gal.      30     646,440
10  gal. (40#)     9.2 gal.      40     861,920