FAQ
Short answers to the most common “what is this actually doing?” questions.
What does “switchover temperature” mean?
It’s the outdoor temperature where the modeled cost per delivered MMBTU is equal for the heat pump and your furnace. Above that point, the heat pump is cheaper (in this simplified cost model).
Why do I need both electricity and fuel prices?
Because the comparison is a unit-cost problem: electricity drives heat pump cost; gas/propane price drives furnace cost. Without both, the balance point cannot be computed.
What is COP and why is it temperature-dependent?
COP (Coefficient of Performance) is delivered heat divided by electric input. In cold air, the heat pump has less heat to extract, so COP typically drops as outdoor temperature drops.
Is the furnace cost temperature-dependent?
This calculator treats furnace cost as constant with temperature using AFUE. Real-world losses can vary, but AFUE is a standard, comparable efficiency input.
Does this include demand charges, TOU rates, or defrost?
No. This is a static, client-side model that compares energy unit costs. If you have time-of-use or demand pricing, use the scenario pages and adjust inputs accordingly.