In recent years, heat pumps have become one of the most important technologies in modern building services engineering. Rising energy prices, stricter energy regulations and growing interest in renewable energy have all contributed to an increasing number of people considering heat pump heating for both new-build homes and renovation projects.
However, many people get stuck at the very first step. What exactly is an air-to-water heat pump? How does it differ from an air-to-air system? When is it worth considering a geothermal solution? And is there really such a thing as a hybrid heat pump?
In this guide, we provide a detailed overview of the main types of heat pumps, their advantages and disadvantages, and their ideal applications, to help you decide which system is best suited to your property.
What is a heat pump?
A heat pump is a device that uses thermal energy extracted from the environment (air, ground or water) to heat and cool buildings and to produce domestic hot water.
The operating principle It’s simple: the system does not generate heat, but rather „transfers” the thermal energy already present in the environment from one place to another. Even in the cold winter air or in the ground, there is a significant amount of energy that can be harnessed with the right technology. This is precisely why the heat pump is currently considered one of the most economical and environmentally friendly heating solutions.
The energy efficiency of heat pumps is generally characterised by the COP and SCOP values. These indicate how many units of thermal energy the system can produce for every unit of electrical energy consumed.
An overview of heat pump types
Heat pump types are primarily distinguished on the basis of the heat source and the medium through which energy is transferred.
| Type | Heat source | Heating | Cooling | HMV | Capital expenditure |
|---|---|---|---|---|---|
| Air-water | Outside air | Yes | Yes | Yes | Medium |
| Air-to-air | Outside air | Yes | Yes | No | Low |
| Geothermal | Soil | Yes | Yes | Yes | Tall |
| Hybrid | Further sources | Yes | It depends on the type | Yes | Medium–high |
Although all these systems operate on the same basic principle, they differ significantly in terms of capital costs, efficiency and areas of application.
Air-to-water heat pump
An air-to-water heat pump utilises energy from the outside air and transfers it to a water-based heating system. This is currently the most common type of heat pump in Hungary.
How does it work?
The outdoor unit extracts thermal energy from the outside air. It uses a refrigerant to raise this to a higher temperature and then transfers it to the water circuit of the heating system. The heated water then:
- can power underfloor heating
- can heat radiators
- can operate fan coil units
- can produce domestic hot water
What types of buildings is it ideal for?
An air-to-water system is a particularly good choice for newly built detached houses, for modern, well-insulated buildings, in conjunction with underfloor heating systems, and for low-energy properties.
Advantages
- no ground drilling is required
- can be installed relatively quickly
- can also be used for cooling
- Tariff H is available to
- good value for money
Disadvantages
The system’s performance depends to some extent on the outside temperature. In very cold weather, efficiency may be reduced, although modern units are capable of operating even at around -20 °C.
When should you choose this option?
For most detached houses in Hungary, this is currently the best solution in terms of investment costs and operational efficiency.
Air-to-air heat pump
An air-to-air heat pump transfers heat extracted from the outside air directly into the air inside the room. Many people are unaware of this, but modern inverter air conditioning systems are actually air-to-air heat pumps: the operating principle is practically the same. The outdoor unit extracts energy from the outside air, and the indoor unit then transfers this to the air in the room. The difference is that there is no water circuit here.
When is it a good choice?
It can be particularly advantageous in smaller flats, holiday homes and weekend cottages, primarily as a temporary or supplementary heating solution.
Advantages
The key benefits of the system:
- low investment cost
- quick installation
- efficient cooling and heating
- no separate plant room is required
Disadvantages
Direct air heating does not provide the same level of comfort for everyone as underfloor heating or a radiator system. A further limitation is that it is not suitable on its own for producing domestic hot water. In larger detached houses or buildings comprising several rooms, it is often insufficient on its own, so it is advisable to combine it with another system.
Geothermal heat pump
A geothermal heat pump uses the constant temperature of the ground or deeper layers of the earth as a source of energy. Geothermal systems generally operate at the highest efficiency, but they also require the largest initial investment.
Ground-penetrating radar system
A ground-source heat pump extracts heat from the ground via vertical boreholes. The boreholes can be as deep as 80–150 metres. The temperature of the deeper layers remains relatively constant throughout the year, so the system’s performance is less dependent on the weather.
Ground-source heat pump system
A ground-source heat pump with a horizontal pipe system harnesses the thermal energy of the ground. In this case, there is no need for deep drilling, but a large plot of land is required.
The main advantages of geothermal systems:
- extremely high efficiency
- low running costs
- long service life
- weather-independent operation
Disadvantages
The cost of the project could be substantial, and the construction work may take longer due to drilling and the need to obtain permits.
When is it cost-effective? For large-scale buildings, institutions and industrial premises.
Hybrid heat pump
A hybrid heat pump combines several heat-generating systems – such as a heat pump and a gas boiler – into a single controlled system.
How does it work?
The control system always selects the heat generator that is operating most efficiently at any given moment. In milder weather, the heat pump is used, whilst in extremely cold conditions, the boiler can assist the system.
Heat pump and gas boiler combination
This is the most common hybrid solution today. It can be particularly advantageous for properties where a working gas boiler and a radiator system are already in place, or where a complete modernisation in a single phase would be too costly.
Advantages:
- a phased transition is possible
- lower investment costs
- greater operational reliability
Disadvantages:
- a more complex system
- greater maintenance requirements
- does not make full use of the benefits of renewable energy
Which heat pump should you choose? – Factors to consider
The choice of the right heat pump is determined by the building’s energy efficiency, the heating system, the site conditions and the budget.
- Newly built detached house: In most cases, a combination of an air-to-water heat pump and underfloor heating proves to be the best solution.
- Refurbished detached house: If the insulation is adequate, an air-to-water system can also be a good choice.
- Old radiator system: In all such cases, a detailed thermal analysis is required. Not all radiator systems are suitable for heat pump operation.
- Flat: An air-to-air heat pump – in other words, an air-conditioning system optimised for heating – is often the most cost-effective solution.
- Holiday home: Air-conditioned heating may also be the most cost-effective option for buildings used only seasonally.
- Industrial and commercial buildings: In this case, a bespoke design is required, taking into account the size of the building, the technical requirements and energy consumption.
Heat pump comparison
The table below provides a quick overview of the differences between the various systems.
| Criterion | Air-water | Air-to-air | Geothermal | Hybrid |
|---|---|---|---|---|
| Capital expenditure | Medium | Low | Tall | Medium–high |
| Efficiency | Tall | Tall | Very high | Variable |
| Cooling | Yes | Yes | Yes | It depends on the type |
| Hot water production | Yes | No | Yes | Yes |
| Installation requirements | Medium | Low | Tall | Medium |
| Retrieval | Good | Good | Longer | Variable |
For most family homes, an air-to-water system offers the best balance between initial investment and savings.
Common misconceptions about types of heat pumps
The heat pump only works with underfloor heating
That’s not true. Many radiator systems can also be adapted for heat pump operation.
It doesn't work properly in winter
Modern systems are now specifically designed for cold climates and can operate even at temperatures below -20 °C.
An air conditioner is not considered a heat pump
In fact, inverter air conditioners optimised for heating are a type of air-to-air heat pump.
A geothermal system is always the best choice
Although it is highly efficient, the high upfront costs mean that it is not always the most cost-effective solution.
Frequently asked questions
Which is the best type of heat pump?
There is no one-size-fits-all solution. The ideal system always depends on the specific characteristics of the building.
What is the difference between an air-to-water heat pump and an air-to-air heat pump?
The air-to-water system operates a water-circulating heating system, whilst the air-to-air system heats the air in the rooms directly.
What type of heat pump is suitable for radiator heating?
Air-to-water heat pumps, which are capable of delivering higher flow temperatures, are most commonly used.
Is it worth installing a geothermal heat pump?
This is certainly the case for energy-intensive buildings and long-term use, but the payback period requires a specific calculation.
Can you also use a heat pump for cooling?
Yes. Most modern systems are capable of operating in cooling mode as well.
Summary
When choosing the right heat pump system, the decision always depends on the building’s technical specifications, energy requirements, available budget and long-term objectives.
For most detached houses in Hungary today, air-to-water heat pumps offer the best value for money, whilst geothermal systems are primarily justified in larger or premium-category projects. For flats and smaller buildings, air-to-air heat pumps – that is, modern inverter air conditioning systems – can be a cost-effective alternative.
Before making a decision, it is worth requesting an on-site assessment and an energy calculation from an expert. A well-designed heat pump system can ensure low running costs, a high level of comfort and environmentally friendly operation for decades to come.
Not sure which type of heat pump would be best for your property? SMARTAIR’s experts can help you assess your building’s specifications and choose the best solution from both a technical and financial perspective.