Energy source cost comparison based on expected winter 2004/5 rates - Vashon Island, WA
Oct 9, 2004
Bob Powell
cost/
(efficiency) realized winter
btu/unit AFUE btu/unit cost/unit cost/Mbtu month
heat pump (ground) 3413 btu/kWh 3.3 11263 $0.07 /kWh $0.006 $45
heat pump (air-air) 3413 btu/kWh 2.2 7509 $0.07 /kWh $0.009 $67
wood 19000000 btu/cord 0.7 13300000 $125.00 /cord $0.009 $68
natural gas 100000 btu/therm 0.95 95000 $1.20 /therm $0.013 $91
oil 140000 btu/gal 0.85 119000 $2.00 /gal $0.017 $121
resistive electric 3413 btu/kWh 1 3413 $0.07 /kWh $0.021 $148
propane 91600 btu/gal 0.9 82440 $2.25 /gal $0.027 $197
Cost/month is hypothetical for Dec-Mar, for well-insulated small house, constant 10,000 btu/h load
Wood vs. heat pump - if wood isn't "free" the heat pump is cheaper
Wood heat assumes modern sealed stove, burning typical northwest softwood mix
Return to the 70's and past - straight resistive electric is no longer the most expensive heat