How the calculation works
Useful heat in MMBtu = therms × 0.1 × furnace efficiency/100. Heat-pump kWh = useful heat ÷ 3.412 ÷ seasonal COP × 1,000. Compare therms × $/therm against heat-pump kWh × cents/kWh ÷ 100. Capital, maintenance, fixed charges and backup differences are outside this fuel-only calculation.
Use inputs you can defend
Read the units and use a consistent billing period. Defaults are examples; replace them with values relevant to your decision. If a cost is unknown, the result cannot establish that it is zero. Keep excluded charges in a separate budget and compare the same service scope before judging two alternatives. You can print this page for your own records without creating a website inquiry.
Put heating fuels on the same basis
One therm is 0.1 MMBtu. Useful heat from gas is therms multiplied by 0.1 and by the furnace’s efficiency as a decimal. For a heat pump, divide useful heat in MMBtu by 3.412 and by seasonal COP, then multiply by 1,000 for kWh. COP describes heat output relative to electric input, not a furnace efficiency percentage. Keep units visible to avoid a tenfold or hundredfold error.
Use seasonal performance, not one ideal condition
Outdoor temperature, equipment selection, building load, controls and backup operation affect actual performance. Ask a qualified contractor for a design appropriate to the building and climate. Include the energy used by backup heat where relevant. A single catalogue COP can be misleading as an annual assumption. Evaluate comfort and ability to meet cold-weather loads alongside operating cost.
Distinguish avoided cost from remaining cost
If the gas connection remains for cooking, hot water or backup, fixed gas charges may remain. Electrical service upgrades, installation, maintenance and cooling benefits can also affect the comparison. Present the fuel-only calculation as one part of the analysis, not total ownership cost. Compare replacement timing and expected useful life before concluding that a working system should be removed.
Keep the inputs private
These calculations run on this page using your browser. They do not save values to local storage, attach figures to a review request or send them to a server. If you choose to ask a question, the review link may select only the inquiry type. Closing or refreshing the page discards your edits. The print button opens your browser’s print dialog.
Sources & further checks
Primary references checked for this guide on October 15, 2026. Follow the source for current tariffs, eligibility and program terms; rates here are not live offers.