When a central air conditioner fails, the heat pump vs central AC question comes up fast, usually on a hot day with a quote in hand. Clement Boston Heat Pumps replaces failed AC systems with ducted heat pumps on the same ducts, and the decision is simpler than it looks: you’re choosing between cooling alone and cooling plus heat.
How the two machines differ
They’re nearly the same machine. A heat pump is a central AC with a reversing valve that flips the refrigerant flow, so the outdoor coil gathers heat in winter instead of dumping it.
| Central air conditioner | Ducted heat pump | |
|---|---|---|
| Cooling | Yes | Yes, the same way |
| Heating | No | Yes, from the same outdoor unit |
| Key extra parts | None | Reversing valve, defrost controls, heating-rated coil |
| Runs in winter | No | Yes, so it carries more hours each year |
| Mass Save rebate | None for an AC | Basic, partial-home or whole-home, depending on the fuel it replaces |
| Controls | Cooling thermostat | Heat pump or dual fuel thermostat with backup heat lockout |
What a heat pump adds, and what it costs
The heat pump costs more than a like-for-like AC, because the outdoor unit and controls do more. Its value is the heating it takes off the furnace, boiler or baseboard.
Pricing the swap
Our typical range for a whole-home heat pump on ducts we can reuse is $15,000 to $28,000 and up before rebates. A system that only replaces the AC and leaves a furnace in charge of cold nights is usually smaller in scope. The written estimate prices both when you ask.
The parts that have to match
A heat pump isn’t a drop-in outdoor unit. The outdoor unit, the indoor coil or air handler, the line set and the thermostat work as a matched system.
- Indoor coil or air handler: must be rated for heating and matched to the outdoor unit’s capacity.
- Line set: newer systems use lower-impact refrigerants such as R-454B, so old lines are tested or replaced; see the refrigerant change.
- Controls: a thermostat that runs the reversing valve, defrost and backup heat.
- Ducts: heating asks more of the ducts than cooling did, so we measure static pressure and returns.
If you have a furnace
A furnace with central AC is the easiest heat pump conversion there is. The heat pump replaces the AC and either takes over the heating or shares it.
Two ways to set it up
- Dual fuel: the heat pump heats most of the winter and the furnace takes the coldest hours. With an integrated control, it earns Mass Save’s partial-home rebate. See dual fuel heat pumps.
- Whole-home: the furnace comes out and the heat pump carries everything. See gas furnace to heat pump.
If you have an attic AC and a boiler
Some older houses heat with a boiler and cool the top floor with an attic air handler. That attic system can become a heat pump that heats the upper floor too.
What to check first
Attic ducts that only ever cooled sit in a cold space in winter. We check their insulation, the ceiling registers’ throw and the return placement, since warm air from the ceiling has to reach the floor. Closing attic registers for winter isn’t needed once the system heats. See attic air handler heat pumps.
How the rebate changes with the setup
The rebate depends on what the heat pump replaces, not on the AC it replaces.
- Heat pump replacing only the AC, with no heating displaced: basic rebate, $250 a ton up to $2,500
- Heat pump sharing heat with a kept furnace or boiler on an integrated control: partial-home, $1,125 a ton up to $8,500 for systems installed through 2026
- Heat pump carrying all the heat, old system out: whole-home, $2,650 a ton up to $8,500 for systems installed through 2026
The per-ton amounts step down for systems installed from January 1, 2027. See Mass Save heat pump rebates.
Sizing: don’t copy the old AC
An old AC’s tonnage is a poor guide, and heating sets a different target. A room-by-room load calculation sizes for both, and for a heat pump the heating load at your design temperature usually governs.
An oversized unit short-cycles and leaves summer air clammy. Read our sizing guide before comparing quotes.
Living with a heat pump instead of an AC
An AC rests from October to May; a heat pump works all year. That changes the upkeep more than the day-to-day feel.
What’s different
- Filters: changed on a schedule through the winter too, not just before summer
- Outdoor unit: kept clear of snow, leaves and drifts, on a stand that lets defrost water drain
- Thermostat: set for heat pump operation, with the backup heat lockout in place; see heat pump thermostats
- Yearly check: coil, drain, refrigerant pressures and the defrost cycle
A yearly visit covers those; our maintenance service lists what it includes.
When an AC alone still makes sense
If you plan to keep a sound furnace for heating, rarely use cooling and want the lowest price today, a central AC is a reasonable choice. The trade-off is buying a machine that sits idle eight months a year.
For most houses replacing a failed AC, the heat pump is the better use of the same ducts. Our replace AC with a heat pump page covers the job; call us or send the form to book a visit.