Why Natural Gas?
Liquefied petroleum gases (LPG) consist primarily of propane and butane, and are usually obtained as a byproduct of oil refinery operations or by stripping natural gas. Propane and butane are gaseous under usual atmospheric conditions, but can be liquefied under moderate pressures at normal temperatures. (Propane is NOT Natural Gas in Bottles, as many people think; Natural Gasis mostly Methane.)
Commercial propane consists primarily of propane but generally contains about 5 to 10% propylene. It has a heating value of about 21,560 Btu/lb, about 2,500 Btu/ft 3 of gas, or about 91,000 Btu/gal of liquid propane. At atmospheric pressure, commercial propane has a boiling point of about 40°F. The low boiling point of propane allows it to be used during winter in the northern United States and in Canada. Tank heaters and vaporizers permit its use in colder climates and where high fuel flow rates are required. Propane is available in cylinders, bottles, tank trucks, or tank cars. Propane-air mixtures are used in place of natural gas in some small communities where natural gas tranmission pipes are not available and by some natural gas companies to supplement normal supplies at peak loads.
2,500 BTUs/Cubic Foot
1 CCF Natural Gas = about 1.1 Gallons Propane
Fuel Cost Conversion Formulas:
Gallon Propane x 1.1 = CCF Natural Gas
CCF Natural Gas / 1.1 = Gallon Propane
If Propane costs $1.50 Gallon, the BTU equivalent cost of Natural Gas would be $1.50 x 1.1 = $1.65 per CCF.
If Natural Gas is $1.00 per CCF, then Propane would have to cost = $1.00 / 1.1 = $0.909 per Gallon to match the BTU cost value of Natural Gas.
Source: Bob Fegan; ASHRAE Handbook Fundamentals 200