Heat pump compared to natural gas boiler in Maine

Questioner: With CMP hiking rates, is a heat pump still efficient enough to cost less than running my gas boiler?

Intelligent Tinkering: It depends on the heat pump and boiler specs. But generally, if you calculate your annual gas consumption from the bill, multiply it by either 91,500 BTUs per gallon (propane) or 1050 BTUs per cubic foot (natural gas), times the percentage efficiency of the boiler expressed as a decimal (usually about 96% for a modern boiler), you'll get your heating season BTU needs (BTUs per year). You then need to divide that by the BTUs/hour capacity of the heat pump (the rated capacity on the outside of the box, usually expressed as a few thousand BTUs/hour, so say 18,000 BTUs/hour, or something like that) and you'll get the estimated annual hours of full load running time for the heat pump. From that, using amps or watts draw of the pump (watts is amps times volts and a watt hour is a watt sustained for an hour), you can estimate the kWh needs and then the kWh cost. You can figure 20% either way, especially for an inverter model pump, because the mid load efficiency may be more or less than the full load.