Heating & Cooling
How a heat pump works
The short answer
A heat pump uses a refrigerant cycle to move heat rather than burn fuel. In summer it pulls heat out of your home and releases it outside (just like an AC); in winter a reversing valve flips the cycle so it pulls heat from the outdoor air and releases it inside. Because it relocates heat instead of creating it, it can deliver more heat energy than the electricity it uses, efficiency rated by SEER2 for cooling and HSPF2 for heating.
What a heat pump actually is
A heat pump is a single system that both heats and cools by transferring heat rather than generating it. It looks much like a central air conditioner, an outdoor unit, an indoor coil, and a refrigerant loop connecting them, and in cooling mode it behaves exactly like one. The difference is that a heat pump can also run that process in reverse to heat your home.
The key idea: even cold air contains heat energy. A heat pump’s refrigerant is cold enough to absorb that heat from the outdoor air, then concentrate and release it indoors. It’s the same principle that lets your fridge pull heat out of food and dump it into your kitchen, just scaled up and made to switch directions.
The refrigerant cycle, step by step
Four components do the work, and the refrigerant changes between liquid and gas as it loops through them:
- Evaporator coil, cold refrigerant absorbs heat from the air passing over it and boils into a low-pressure gas.
- Compressor, squeezes that gas, which raises its pressure and temperature so it’s now hotter than where the heat needs to go.
- Condenser coil, the hot, high-pressure gas releases its heat and condenses back into a liquid.
- Expansion valve, drops the pressure, cooling the refrigerant back down so it’s ready to absorb heat again, and the loop repeats.
Nothing is “burned”, the system simply picks up heat in one location and lets it go in another. See refrigerant, evaporator coil, and condenser in the glossary.
How one unit both heats and cools (the reversing valve)
The piece that separates a heat pump from a plain air conditioner is the reversing valve. It changes the direction the refrigerant flows, which swaps the roles of the two coils:
- Cooling (summer): the indoor coil absorbs heat from your home and the outdoor coil releases it outside.
- Heating (winter): the valve flips, so the outdoor coil absorbs heat from the outside air and the indoor coil releases it into your home.
One piece of equipment, two jobs, which is why a heat pump can replace both a furnace and an AC, or pair with a furnace in a dual-fuel setup.
Why moving heat beats burning fuel
A furnace can never turn more than 100% of its fuel into heat, a 96% AFUE furnace is near the ceiling. A heat pump plays a different game: because it’s relocating existing heat rather than creating it, it can deliver two to three times more heat energy than the electricity it consumes. That’s why heat pumps are so efficient, especially in milder shoulder-season weather.
Efficiency is measured two ways: SEER2 rates cooling performance and HSPF2 rates heating performance. Higher numbers mean lower operating costs, which is what you feel on the monthly bill.
Do heat pumps work in Minnesota winters?
Yes, modern cold-climate heat pumps are engineered to pull usable heat from the air well below zero, a world apart from the units of a decade ago. As it gets extremely cold, capacity drops, so many Minnesota homes run a heat pump as the efficient primary system with a furnace or electric heat as backup for the coldest stretches (a “dual-fuel” setup). You’ll also notice an occasional defrost cycle, where the unit briefly melts frost off the outdoor coil.
We dig into sizing, backup heat, and real-world performance in our guide on heat pumps in Minnesota winters, and compare options in AC vs. heat pump.
How Gray Duct does it
Whether a heat pump is the right call depends on your home, your existing system, and how you want to handle the coldest weeks. Gray Duct sizes every system with a proper Manual J load calculation and gives you an honest recommendation, heat pump, dual-fuel, or a straightforward AC-and-furnace pairing, never a one-size sales pitch.
- Heat pumps sized with a Manual J load calculation, not a rule of thumb
- Cold-climate heat pumps selected for Minnesota winters
- We install Heil and Goodman heating and cooling equipment
- In-house, veteran-owned team, licensed, bonded and insured in MN
Frequently asked questions
- Is a heat pump the same as an air conditioner?
- In cooling mode, essentially yes, the refrigerant cycle is identical. The difference is the reversing valve, which lets a heat pump also run the cycle backward to heat your home, so one unit does both jobs.
- How efficient is a heat pump?
- Because it moves heat instead of creating it, a heat pump can deliver two to three times more heat energy than the electricity it uses. Cooling efficiency is rated by SEER2 and heating efficiency by HSPF2, higher is better.
- Will a heat pump keep my house warm in a Minnesota cold snap?
- Modern cold-climate heat pumps produce heat well below zero, but capacity falls as it gets colder. Many MN homes use a dual-fuel setup, a heat pump for efficiency most of the year plus a furnace for the coldest stretches. See our heat pumps in Minnesota winters guide.
- Does a heat pump replace my furnace?
- It can be the sole heating and cooling source, or it can pair with a furnace in a dual-fuel system that switches to gas heat when it's most economical. We'll run a load calculation and walk you through which fits your home.
Keep learning
Related & next steps
Thinking about a heat pump?
We'll size it with a real load calculation and tell you honestly whether a heat pump, dual-fuel, or a standard system is the smartest choice for your Twin Cities home. Book a free estimate. See where we work.