How does a heat pump work? The principle explained simply

  • David Klibani
  • 6 min čítanie

A heat pump can heat a house even when it’s cold outside. It doesn’t work by generating heat through the combustion of fuel. Instead, it extracts heat from the outside air, adjusts its temperature and transfers it into the house. How does it all work?

A heat pump does not produce heat, but transfers it

The principle is easiest to explain using a fridge as an example. A fridge extracts heat from inside itself and discharges it outside. That is why it feels warm at the back, even though it maintains a low temperature inside. A heat pump works in a similar way, only in the opposite direction. Instead of extracting heat from the air inside the house, it extracts it from the outside air and transfers it indoors.

And yes, it works even when the temperature outside is below freezing. Even cold air still contains heat. A heat pump can utilise this heat and transfer it to the house’s heating system.

How does the heat get from the air into the house?

The whole process is facilitated by a closed refrigerant circuit. You don’t need to know the technical details to understand the basic principle. The refrigerant is able to absorb heat from the surrounding air. When it warms up, it flows into the compressor, which compresses it, thereby raising its temperature to a level at which the heat can be used for heating.

The heat obtained in this way is then transferred to the water in the heating system. This water then flows into underfloor heating, radiators or is used to heat domestic hot water. After the heat has been transferred, the refrigerant cools down and the whole process repeats itself.

What happens inside a heat pump?

The entire cycle can be simplified into four steps.

1. The refrigerant absorbs heat

The outdoor unit extracts heat from the air. The refrigerant inside the unit absorbs this heat, even when it is cold outside.

2. The compressor raises the temperature

The heated refrigerant flows into the compressor. The compressor compresses it, thereby raising its temperature to a level at which the heat can be used for heating.

3. The heat is transferred to the house

The hot refrigerant transfers the heat it has absorbed to the water in the heating system. The water then flows into the house, providing heating or hot water.

4. The cycle repeats

After transferring the heat, the refrigerant returns to its original state and the whole process begins again. A heat pump can thus continuously extract heat from the outside air and supply it to the house.

You therefore need not worry that the heat from the outside air will simply ‘run out’. The system operates with a constant flow of air and repeats the entire process according to the house’s needs.

How much electricity does a heat pump use?

A heat pump requires electricity, but this electricity is not used to generate all the heat. It primarily powers the compressor, fan and other parts of the system that enable heat to be transferred. This is precisely why a single unit of electricity consumed can produce several times more heat.

The ratio between the heat supplied and the electricity consumed is known as the COP. The higher this ratio, the more heat the unit can supply whilst consuming the same amount of electricity. In practice, however, the actual consumption depends on the conditions in which the heat pump is operating, the outdoor temperature and the heating system in the house.

Does a heat pump work in freezing conditions?

This is one of the most frequently asked questions when choosing a heat pump. The answer is yes. An air-to-water heat pump is designed to extract heat from the air even at low outdoor temperatures.

However, as the outdoor temperature drops, the operating conditions change. It is therefore important to choose the right model and tailor its capacity to the specific house. Among EnergySky’s solutions, for example, is the  SKY Top-Blow Monoblock, which is an air-to-water heat pump. When making your choice, however, you should not focus solely on the unit itself. The design of the entire heating system is also important.

A heat pump does not just have to heat

A heat pump can also operate in reverse. In summer, it can extract heat from the interior and discharge it outside, so it can also be used for cooling. The principle is similar to that of air conditioning. Depending on the settings, the unit moves heat in the direction you need at any given time.

This is particularly practical in new-builds or homes where a single system is expected to provide heating in winter and a more comfortable temperature in summer.

Which heat pump should you choose?

Not every house has the same options for installing a heat pump. Sometimes the space around the house is important, other times it’s the method of air exhaust or the available installation space. For more compact installation spaces, the STANDARD Side-Blow Monoblock may be a suitable alternative.

If you want to combine heating with hot water production in a single solution, EnergySky offers the ALL-IN-ONE Heating & Hot Water system. However, the specific model should be chosen based on the house itself, not just on the appearance of the unit or its name. The decisive factors are the size of the house, the heating method, its heat loss and the conditions at the installation site.

Heat pumps in practice

The principle behind a heat pump is actually simpler than the technical terms at the start might suggest. The unit extracts heat from the outside air, uses a refrigerant and a compressor to raise its temperature, and transfers it to the house.

However, proper functioning also depends on how the entire system is designed. A good heat pump must be suited to the specific house and its heating requirements.

If you’d like to explore the various options, you can find the full range of EnergySky models and solutions here. We’ll be happy to help you choose a solution that suits your home and your heating system.