How a heat pump works
A heat pump moves heat between inside and outside using refrigerant and electricity — it doesn't burn anything. In summer it's an air conditioner; in winter it's an air conditioner running in reverse.
The kitchen analogy: your refrigerator pumps heat out of the box and into the room. A heat pump in winter does the same trick outdoors — it pumps heat out of the cold outside air and into your house. And yes, even cold air holds heat to move; the refrigerant just has to be colder still to grab it.
One refrigerant loop, both directions
Evaporator absorbs heat
Refrigerant pulls heat from the air on one side — indoors in summer, from the outdoor air in winter.
Compressor squeezes it hot
Compressing the refrigerant concentrates that heat, making it hotter than the air it's about to warm.
Condenser releases heat
The hot refrigerant dumps its heat on the other side — outdoors in summer, into your home in winter.
Expansion valve resets
The refrigerant drops in pressure and temperature, ready to absorb heat again. The loop repeats.
Summer versus winter is simply the direction the loop runs — same four stops, reversed.
The reversing valve makes it a heat pump
One component flips the loop's direction — the reversing valve. That's the entire difference between a heat pump and a plain AC. When it shifts modes you may hear a whoosh or a click from the outdoor unit; that's normal, not a fault. When the valve fails, it gets stuck in one mode — which is why a heat pump can end up blowing cold air in winter.
Defrost, balance point, and cold-climate truth
Defrost mode
In cold, the outdoor coil frosts over, so the system briefly reverses to melt it — steam rises outside and the vents blow cool for 5–15 minutes. Normal, not broken.
Balance point
Below roughly 25–35°F, output starts to drop and backup heat strips kick in to fill the gap — which is why the electric bill can spike in a cold snap.
Cold-climate models
Modern cold-climate heat pumps hold full output well below freezing, into the negatives — a real option even where winters are hard.
The steaming, cool-air-for-a-few-minutes behavior is the same one covered in why a system blows cold air — worth knowing before it startles you.
Types: air-source, geothermal, mini-split
Air-source (ducted)
The default — it exchanges heat with the outdoor air and uses your existing ducts.
Geothermal
Exchanges heat with the ground through buried loops. The most efficient, and the highest upfront price.
Ductless mini-split
Wall-mounted heads heat and cool zone by zone — the go-to for homes without ducts. See the mini split hub.
Efficiency, honestly
The whole efficiency story in one line: for every unit of electricity, a heat pump moves 3–4 units of heat. Compare that to electric resistance heat (1 unit in, 1 unit out) or a gas furnace (about 0.95 out).
Heat pump ........ 1 kWh in → 3–4 units of heat
Electric strip ... 1 kWh in → 1 unit of heat
Gas furnace ...... burns fuel → ~0.95 of it as heat
Where deep cold meets cheap gas, the math can flip — the full comparison is on heat pump vs furnace.
Common questions
How long do heat pumps last?
Typically 10–20 years, often a bit shorter than a furnace because a heat pump works year-round — heating and cooling — rather than one season. Regular maintenance stretches it.
Do heat pumps use a lot of electricity?
Less than what they replace. Because a heat pump moves heat rather than making it, it delivers several units of heat per unit of electricity, so it uses far less power than electric resistance heat for the same warmth.
What's the main advantage over a furnace?
One machine heats and cools, and it does it efficiently by moving heat instead of burning fuel — no combustion, no flue, and lower running costs in most climates.
Does a heat pump cool as well as an AC?
Yes — in cooling mode it is essentially the same machine as an air conditioner, running the same refrigerant cycle. The reversing valve is the only real difference.
Why is my heat pump steaming or blowing cool air in winter?
That's almost always a normal defrost cycle: the outdoor coil iced up, so the system briefly reverses to melt it, which produces steam outside and cooler air from the vents for 5–15 minutes. It's not a fault.
Do I need backup heat?
In milder climates, a modern heat pump carries the whole season. In sustained deep cold, output drops at the balance point and a backup heat source — electric strips or a gas furnace in a dual-fuel setup — takes over.
One call routes you to a licensed local contractor: (888) 810-2291.