A heat pump is a heating and cooling system that moves heat rather than generating it. In summer it works like an air conditioner, pulling heat out of the house. In winter it reverses, extracting heat from outside air or the ground and delivering it indoors.
That reversal is the whole idea, and it is why a heat pump can deliver more heat energy than the electrical energy it consumes. A furnace burning fuel can never exceed 100 percent of the energy it consumes. A heat pump routinely delivers two to four times its electrical input, because it is relocating existing heat rather than creating it.
The ratings you will be quoted
- HSPF2 rates heating season efficiency. Higher is better.
- SEER2 rates cooling season efficiency. Higher is better.
- COP, coefficient of performance, is the instantaneous ratio of heat delivered to energy consumed. A COP of 3 means three units of heat per unit of electricity.
The numbers with a 2 are the current testing standard. Older SEER and HSPF figures are not directly comparable, so be careful comparing a new quote against an old brochure.
Types
Air source pumps draw heat from outdoor air. Most common, least expensive to install.
Ducted versus ductless. Ductless mini-splits serve individual zones without ductwork, which suits additions, older homes, and rooms that never worked. Ducted systems use existing distribution, if the ducts were designed properly.
Ground source, often called geothermal, draws from stable underground temperatures. Far more efficient, far more expensive to install, because it requires excavation or drilling.
Cold climate models are engineered to maintain useful output at low outdoor temperatures. This is the category where the technology changed most in the last decade, and where outdated advice does the most damage.
Where buyers get hurt
Sizing. This is the one that ruins installations. A heat pump sized by square footage instead of a Manual J load calculation short cycles, fails to dehumidify, and leaves some rooms permanently wrong. Oversizing is the single most common installation defect in this category, and no amount of equipment quality compensates for it.
Backup heat that quietly runs the bill up. Many installations include electric resistance strip heat for the coldest hours. If the system is configured to lean on it, or if the thermostat calls for it aggressively, winter bills can arrive much higher than promised. Ask specifically how often backup heat is expected to engage and what it costs when it does.
Old assumptions about cold weather. The belief that heat pumps stop working when it gets cold comes from equipment sold decades ago. Cold climate models have moved well past that. The failure mode now is usually a system sized or configured badly, not a system incapable of the job.
Ductwork nobody assessed. Installing efficient equipment onto undersized or leaky ducts inherits every problem the old system had. The new unit gets blamed for the old distribution.
The pattern across all four: a heat pump is supposed to make the house quieter, steadier, and cheaper to live in. When it does not, the cause is almost always what happened before the equipment was chosen, not the equipment.