Heat pump cooling vs air conditioningUsing a reversible heat pump to cool, or fitting a separate AC system
If you want a cooler home in summer you have two broad options: use a reversible heat pump that already heats your home, or install a separate air-conditioning system. This page compares the two so you can see where each makes sense.
Updated
They are closely related technologies
A reversible heat pump and an air conditioner work on the same principle: a refrigerant cycle that moves heat from one place to another. An air conditioner moves heat out of your home; a reversible heat pump can move heat in or out, depending on the season.
In other words, a reversible heat pump already contains the machinery to cool. The question is usually whether to use it for cooling, or to add a second, dedicated system.
Cooling with a heat pump you already have
If you have a cooling-capable Vaillant aroTHERM or VWL heat pump, cooling can be unlocked by fitting the cooling resistor and having an installer enable the function. There is no second outdoor unit and no second machine to maintain.
The main consideration is how the cooling is delivered indoors. Heat pump cooling typically circulates chilled water, which works well through fan coil units, and less well through ordinary radiators. The system also needs dew-point control to manage condensation — confirm what your setup needs with an installer.
Installing a separate AC system
A standalone air-conditioning system — for example, wall-mounted indoor units fed by their own outdoor unit — is a self-contained way to cool. It is independent of your heating, can be sized purely for cooling, and is a familiar product for installers.
The trade-off is a second system: another outdoor unit, separate pipework, separate maintenance, and additional cost, alongside a heat pump that may already be capable of cooling.
A side-by-side summary. The right choice depends on your existing heat pump and how you want cooling delivered.
| Aspect | Heat pump cooling | Separate air conditioning |
|---|---|---|
| Equipment | Uses your existing heat pump | Additional dedicated system |
| Outdoor units | No extra unit needed | Extra outdoor unit |
| What it needs | Cooling resistor + installer activation | Full AC installation |
| Delivery indoors | Chilled water — fan coils suit best | Direct-expansion indoor units |
| Heating | Same machine heats in winter | Heating handled separately |
| Maintenance | One system to service | Two systems to service |
Frequently asked questions
Is heat pump cooling the same as air conditioning?
They use the same underlying technology — a refrigerant cycle that moves heat. The difference is that a reversible heat pump does both heating and cooling, while a standalone AC system is dedicated to cooling.
Is heat pump cooling as good as a dedicated AC unit?
Both can cool a home effectively. Heat pump cooling depends on suitable emitters such as fan coil units and proper dew-point control. A dedicated AC system is sized purely for cooling. The better fit depends on your home and existing system.
Which is cheaper?
If you already have a cooling-capable heat pump, enabling its cooling can avoid the cost of a second system. A separate AC install is an additional outdoor unit and pipework. The cooling resistor itself costs £47.50; installation costs vary — get a quote from an installer.
Can heat pump cooling work through my radiators?
Not effectively. Heat pump cooling generally needs fan coil units rather than ordinary radiators. A dedicated AC system uses its own indoor units. Check what your home needs with an installer.