What winter actually asks of a heat pump here
Your furnace, whatever kind you end up with, runs about eight months a year in Schuylkill County, October through May. Nobody here is buying a machine for a mild shoulder season. They're buying one to carry most of the year.
The overnight low averages 21°F across December, January and February. That matters because a standard heat pump starts losing ground before it even gets that cold. Below 40°F its heat output falls short of what it's rated for. Below about 35°F it often needs backup heat to keep up. Your average winter night here is below both marks, and so is every one of the roughly 125 nights a year that drop to freezing or colder, about half the nights the heat runs.
A furnace, gas or oil, doesn't have that dip. It makes the same heat on a cold night as it does on a mild one. A heat pump built to the federal minimum will be working below its best range on more than half the nights you run it.
The hardest cold is the smaller part of the picture. Only about 3 nights a year here reach 0°F or below. A heat pump certified as ENERGY STAR Cold Climate has to prove, in third-party testing, that it still makes at least 1.75 units of heat per unit of electricity at 5°F and holds onto most of its 47°F capacity at that temperature. In field tests of these units in occupied homes, backup heat covered only a small share of the load between 0°F and 35°F, and the unit running on backup alone was rare even above 0°F. So the real question for a heat pump here is not the 3 coldest nights. It's the far larger stretch in the 20s and low 30s, and that depends on the specific unit, not on heat pumps as a category.











