At first glance, an aerothermal heat pump and an air conditioner look almost identical — both have an outdoor unit, both use refrigerant, and both can cool a room. This similarity causes real confusion when shopping for a home climate system. Here’s what actually separates them.
The Short Answer
Every air conditioner is built to move heat in one direction only: from indoors to outdoors, to cool a space. An aerothermal heat pump uses the exact same refrigeration cycle but adds a reversing valve, allowing it to move heat in either direction — cooling in summer and heating in winter by extracting warmth from outdoor air, even when it’s cold outside.
In short: a heat pump can do everything an air conditioner does, plus heating — but not every air conditioner can do what a heat pump does.
How Each System Actually Works
Air Conditioner
An AC unit compresses refrigerant, sends it outdoors to release heat (condensation), then cools and expands it before it absorbs heat from indoor air and cycles back out. This process only runs in one direction: heat is always pulled from inside the building and dumped outside.
Aerothermal Heat Pump
A heat pump runs the same compression cycle, but a reversing valve can flip the direction of refrigerant flow. In heating mode, the outdoor coil becomes the evaporator (absorbing heat from outside air, even at low temperatures) and the indoor coil becomes the condenser (releasing that heat indoors). In cooling mode, it operates exactly like a standard air conditioner.
Side-by-Side Comparison
| Factor | Air Conditioner | Aerothermal Heat Pump |
|---|---|---|
| Cooling | Yes | Yes |
| Heating | No (cooling only) | Yes, even in cold weather |
| Core technology | Refrigeration cycle | Same cycle + reversing valve |
| Water heating (DHW) | Not typically | Yes, with air-to-water models |
| Winter usefulness | None — needs separate heating | Fully replaces a boiler or furnace |
| Running cost in winter | N/A (doesn’t heat) | Lower than gas, oil, or resistance electric heating |
| Upfront cost | Lower | Higher, offset by winter savings and subsidies |
| Efficiency metric | SEER/EER (cooling only) | SEER/EER + COP (heating) |
| Best for | Cooling-only needs, hot climates | Year-round heating and cooling, replacing fossil fuel heating |
Why This Confusion Happens
Manufacturers often use «air conditioner» loosely to describe air-to-air systems (mini-splits) that are technically heat pumps, since many modern mini-split units include heating mode by default. This is why it’s worth checking the spec sheet: if a unit lists a heating capacity (BTU or kW) and a COP rating, it’s a heat pump, not a cooling-only air conditioner — regardless of what it’s called in the product name.
Efficiency: Why a Heat Pump Beats Electric Heating
Because a heat pump moves heat rather than generating it, it delivers far more heating energy than the electricity it consumes — typically a COP of 3 to 5, meaning 3 to 5 kWh of heat per 1 kWh of electricity. A standard electric resistance heater, by contrast, has a COP of 1: it can never produce more heat energy than the electricity it uses.
Cost Comparison Over Time
- Upfront: A cooling-only AC is usually cheaper to buy and install.
- Long-term: A heat pump typically costs more initially but replaces both a cooling system and a heating system (boiler, furnace, or electric heaters), often paying back the difference through combined savings, government incentives, and higher efficiency.
Which One Should You Choose?
Choose an air conditioner if:
- You live somewhere with no real heating season
- You already have an efficient heating system and only need cooling
- Budget is limited to cooling needs only
Choose an aerothermal heat pump if:
- You want one system for both heating and cooling
- You’re replacing an aging gas boiler, oil furnace, or electric heater
- You want to lower your carbon footprint and long-term energy bills
- You may qualify for renewable heating subsidies (heat pumps often qualify; standard AC units typically do not)
Frequently Asked Questions
Is a heat pump more expensive to run than an air conditioner?
In cooling mode, running costs are nearly identical since both use the same refrigeration cycle. The heat pump only becomes more valuable once you factor in heating season, where it replaces a separate, often costlier heating system.
Can I convert my existing air conditioner into a heat pump?
No. The reversing valve and heating-rated components must be built into the system from manufacturing — it can’t be retrofitted onto a cooling-only unit.
Do heat pumps work as well as air conditioners for cooling?
Yes. In cooling mode, a heat pump performs identically to a standard air conditioner because it uses the exact same cycle.
Are heat pumps eligible for the same subsidies as air conditioners?
Usually not. Most renewable energy incentives target heat pumps specifically because they displace fossil fuel heating — cooling-only air conditioners typically don’t qualify.