What is latent heat of LPG?

Because LPG is a mixture, the value of the latent heat will depend on the exact composition of the mixture. The main components of LPG are:

• propane - C3H8
• propylene (propene) - C3H6
• isobutane - C4H10
• n-butane - C4H10
• butylene (butene) - C4H8

Since LPG is usually mostly propane and butane, a rough estimate would be in the range of the values for these two components. Note that latent heat is dependent on temperature as well. for the purposes of this answer we will use 30 °F (near the boiling point of butane at atmospheric pressure)

Hvap(propane @ 30 °F) = 163 BTU/lb

Hvap(butane @ 30 °F) = 166 BTU/lb