Part of our guide to Repair or Replace? How to Decide on an Ageing Air Conditioner
These are not two different appliances so much as one appliance with an extra valve. Understanding that makes the decision much simpler than the sales pitch suggests.
A heat pump cools identically to an air conditioner and then runs in reverse to heat. So the real question is not "which cools better" — it is what you heat with now. Replacing electric resistance heat, a heat pump is a clear win. Replacing a cheap gas furnace, it depends on local fuel prices, and a dual-fuel system may beat both.
How a heat pump actually works
Neither device creates cold. Both move heat from one place to another using a refrigerant loop — that is all air conditioning is.
An air conditioner moves heat from inside your house to outside. A heat pump does the same in summer, then flips a reversing valve in winter and moves heat from the outdoor air into the house.
That sounds impossible in cold weather, and it is the point people get stuck on. There is still heat energy in air well below freezing; the refrigerant is simply colder than the outside air, so heat flows into it. It gets harder as temperatures drop, which is why capacity falls in deep cold — not because the physics stops working.
This is why heat pumps beat electric heating so decisively. An electric resistance heater converts one unit of electricity into one unit of heat. A heat pump moves several units of heat using one unit of electricity, because it is not generating the heat at all.
Where each one wins
| Heat pump | Central air + furnace | |
|---|---|---|
| Cooling | Same | Same |
| Heating | Built in | Separate furnace |
| Replacing electric heat | Clear win | Poor |
| Very cold climate | Needs backup heat | Furnace unaffected by cold |
| Cheap natural gas available | Depends on local prices | Often cheaper to run |
| Equipment count | One system | Two systems |
| No gas line to the house | Natural fit | Needs propane or oil |
Climate, honestly
The old advice was that heat pumps suit mild climates only. That is outdated for current equipment but not entirely wrong about the physics.
Mild winters — a heat pump is straightforwardly the better choice. One system, both jobs.
Cold winters — cold-climate heat pumps hold usable capacity far below freezing, and are widely installed in genuinely cold regions. What they need is a plan for the coldest days: either electric backup heat, or a furnace in a dual-fuel arrangement.
Very cold, with cheap gas — dual fuel is often the honest answer. The heat pump handles most of the season efficiently; the furnace covers the extremes.
The number to ask an installer for is the heating capacity at your design temperature — the coldest condition your area actually sees — not the rated capacity at mild conditions. Those are different figures and only one of them matters in January.
Air from a heat pump comes out cooler than air from a gas furnace — comfortably above body temperature, but noticeably below what a furnace produces. Standing in front of a vent, it can feel like a draught even while the room is warming correctly.
Heat pumps also run longer cycles at lower output rather than short blasts, which is more efficient and gives steadier temperatures. Both are normal and neither indicates a fault, but people switching from a furnace regularly report them as problems. Knowing in advance is the difference between adapting and calling a technician.
What actually decides it for most people
- What you heat with now. Electric resistance → heat pump, almost always. Cheap gas → run the numbers or go dual fuel.
- Your climate's coldest realistic week, not its average.
- Whether you have ducts, and their condition. Ductwork is the common hidden cost in either direction, and a leaky duct system undermines whatever you install.
- Local electricity and gas prices. This is the one that varies most between households and gets assumed rather than checked.
- Available incentives. Heat pumps frequently attract utility rebates and tax credits that change the arithmetic. These change often — check current terms rather than an article.
What does not decide it
Cooling performance. They cool the same way. Any claim that one cools better is about the specific equipment, not the type.
Brand. Installation quality — correct sizing, sealed ducts, proper refrigerant charge — affects real-world performance far more than the badge.
The biggest available unit. Oversized equipment short-cycles, dehumidifies poorly and wears faster. Sizing should come from a load calculation of your actual house, not a rule of thumb about square footage.
For what the efficiency ratings on the sticker actually mean, see what a SEER rating really buys you.
This is general information, not professional advice — see our disclaimer.
Frequently asked questions
What is the actual difference?
A heat pump cools exactly like an air conditioner, then reverses in winter to bring heat indoors. An air conditioner only cools, so it needs a separate furnace for heating.
Do heat pumps work in cold weather?
Modern cold-climate models do, well below freezing. Capacity still falls as it gets colder, which is why systems in cold regions include backup heat for the worst days.
Is a heat pump cheaper to run?
Against electric resistance heating, substantially — it moves heat rather than generating it. Against a cheap natural gas furnace the answer depends on local gas and electricity prices, and can go either way.
What is a dual-fuel system?
A heat pump paired with a gas furnace. The heat pump handles mild weather and the furnace takes over when it turns very cold. It suits cold regions with cheap gas.
Can I keep my existing ducts?
Usually yes, if they are in good condition and correctly sized. Ductwork is often the hidden cost in any changeover, so have it assessed before comparing quotes.
Sources
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