I had a heat pump installed a few months ago. The installer set the auxillery heat to take over at 25 degrees. The heat pump has no problem heating my house at this temperature, but I am worried that it is less efficient at these low temperatures than my gas furnace. My worry is not about the money. It is the amount of carbon released. I think my furnace is 78% efficient and the heat pump is 13 seer and hspf 8.5.

Is my heat pump more or less efficient at 25 degrees than my furnace?