Fuel Type Million Btu/Unit (1) Available Unit /million Btu (2) Comment  #2 Fuel Oil 0.143/gallon 8.77 80% efficient  Charcoal 0.0125/pound 107 75% efficient  Coal:     75% efficient  Anthracite 26.3/ton 0.051    Bituminous 28.7/ton 0.046 Low Volatile  Bituminous 24.7/ton 0.054 High Volatile  Subbituminous 19.2/ton 0.069    Lignite 13.9/ton 0.096    Electricity 0.003/kVh (3) 308 95% efficient  Kerosene 0.131/gallon 9.56 80% efficient  Natural Gas 1.05/Mcf (3) 0.839 80% efficient  Propane 2.53/Mcf (3) 1.97 78% efficient  Wood     55% efficient  Apple 29/cord 0.063 L-smoke, L-spark Aspen 17/cord 0.11 M-smoke, H-spark Cottonwood 16/cord/ 0.115 M-smoke, L-spark Elm 20/cord 0.092 M-smoke, M-spark Fir, Douglas 26/cord 0.069 H-smoke, M-spark Hickory 28/cord 0.066 L-smoke, L-spark Maple 22/cord 0.084 L-smoke, L-spark Oak 26/cord 0.069 L-smoke, L-spark Pine, Lodgepole 17/cord 0.106 M-smoke, M-spark Pine, Pinon 31/cord 0.058 M-smoke, M-spark Pine, Ponderosa 19/cord 0.097 M-smoke, M-spark Pine, White 15/cord 0.125 M-smoke, H-spark Spruce, Englem 16/cord 0.114 M-smoke, H-spark   "l-" IS Low,