Frequently Asked Questions About Heat Pumps

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Common questions about heat pumps – expert answers for future and current owners

Heat pumps are one of the most discussed topics in the heating industry today. Interest in them is growing rapidly – as are the number of questions, misconceptions and false beliefs. After years of working with customers, technicians and installers, we know that most people still face the same core issues: how it actually works, what it will cost, when it pays off, what if it freezes, what if it breaks down, and why your neighbor says something different than the manufacturer. This article is an attempt to give as concrete and factually verified answers to these questions as possible – without unnecessary marketing glitz, but with real technical depth.

We cover the most frequently asked questions our customers ask before purchasing, during the selection of a specific model, during installation and after years of operation. If you're looking for a specific sub-topic, such as air-to-water versus ground-to-water comparison, or the installation procedure, we also refer you to other articles in our Knowledge Center, where these topics are explored in depth.

How does a heat pump actually work – the basic principle

This is the first question of almost every customer, and despite that, many struggle with it for months. A heat pump does not produce heat from the air – it transfers it. The same principle is used by your refrigerator, only in reverse. A refrigerator takes heat from the inside and removes it outside. A heat pump takes heat from the outside (from air, ground or water) and transfers it inside the house.

The key is the refrigerant circuit with refrigerant (most commonly R32 or R410A in older units). The refrigerant evaporates at low temperatures (even -20 °C), absorbing heat from the surroundings. The compressor then compresses it, raising its temperature – sometimes up to 60–70 °C. This thermal energy is transferred to the house's heating circuit via the condenser. Expanding the refrigerant in the expansion valve repeats the whole cycle.

An important term that will help you in your selection: COP (Coefficient of Performance). It indicates how many kWh of heat the pump produces for each 1 kWh of electrical energy. A COP of 3.5 means that from 1 kWh of electricity you get 3.5 kWh of heat. In practice, you also encounter the term SCOP (Seasonal COP) – this is an annual average, which is more realistic than the laboratory-measured COP at a fixed temperature.

How much electricity does a heat pump consume?

This is question number one for everyone who is just deciding. And the answer is not simple, as it depends on several factors: the thermal insulation condition of the house, the set power of the pump, the heating distribution system in the house and, of course, the climatic conditions in the given region.

As an approximate example: a standard family house with an area of 150 m² and an annual heat requirement of 15,000 kWh will consume about 4,700 kWh of electricity per year with an air-to-water heat pump with an average SCOP of 3.2. At a price of 0.20 € per kWh, this is about 940 € per year for heating. The same house with gas at a price of 0.08 €/kWh would cost about 1,200 €, but if the gas price is higher or the house is insufficiently insulated, the difference becomes even more pronounced in favor of the heat pump.

The key factor is the temperature of the heating system. Heat pumps work most efficiently at low-temperature systems – floor heating (35–40 °C) is ideal. With a radiator system with a required temperature of 70 °C, performance drops significantly and COP may fall below 2. That is why it is important to assess the existing heating system before installation. More on how to estimate the required power can be found in the article What power of heat pump do I need for my house.

Does a heat pump work in freezing temperatures?

Yes, modern air-to-water heat pumps operate normally even at -15 °C, with top models down to -25 °C outside temperature. Naturally, the colder it is outside, the lower the performance and COP of the pump – this is a physical reality, not a device defect. Manufacturers therefore usually state the nominal power at A7/W35 (outside temperature +7 °C, water output temperature 35 °C), which is a standardized test point.

In practice, this looks like this: a pump with a nominal power of 12 kW at A7/W35 may achieve only 7–8 kW at A-15/W45. Therefore, when dimensioning the system, the so-called balance point is calculated – the temperature at which the pump's power exactly covers the house's heat losses. Below this temperature, an electric booster (bivalent operation) may kick in.

Important notice: at temperatures around 0 to -5 °C, the evaporator on the outdoor unit may freeze. Therefore, the heat pump regularly (every 40–90 minutes) switches into a defrost cycle – this is a normal condition, not a malfunction. It typically lasts 3–8 minutes, during which the refrigerant is reversed and the evaporator is defrosted. Customers sometimes mistakenly report this as a fault, because steam rises from the outdoor unit and heating temporarily stops.

Heat pump for domestic hot water – is it possible?

Yes, and it is one of the most popular ways of using it. Most modern heat pumps combine heating with the preparation of domestic hot water (DHW). This can work in two ways:

Integrated tank directly in the unit – for smaller houses, usually 190–260 liters.
External tank – connecting the heat pump to a boiler via a hydromodule. This brings up the question of setting priorities correctly: should the system prioritize heating or DHW heating? Most controllers handle this automatically according to a schedule.

Practice: for a family of four with average DHW consumption, a 200–250 liter tank is sufficient for daily heating. If you have solar collectors, you can combine them with a heat pump and save even more. To ensure hot water circulation in the household, specialized accessories are used – for example, Hot water circulation kit for models ITEC-T, ATHENA-T, LEGEND, CALIBRA and ATLAS, which ensures that hot water is immediately available even in remote parts of the house without long waiting times. We write more about this topic in the article Integration of hot water circulation with a heat pump – how to do it.

What is the difference between a monoblock and a split system?

This is a technical question that is very practically expressed during installation and operation.

Monoblock is a unit where the entire heat cycle (including the evaporator, compressor and condenser) takes place in the outdoor unit. Only water is led into the house. Advantage: simpler maintenance, no certification is required for work with refrigerant during standard installation. Disadvantage: the pipe between the outdoor unit and the house must be thermally insulated and protected against freezing.

Split system has an outdoor and an indoor unit connected by refrigerant pipes. The refrigerant circulates between the two units, and the heat is transferred to the water only in the indoor unit. Advantage: more efficient heat transfer, lower heat losses, better regulation. Disadvantage: installation of the refrigerant pipe connection requires a technician with F-gas certification.

For family houses in Slovakia, the most common today is a split system with a power of 6–14 kW. Monoblocks are popular especially where the distance from the outdoor unit to the technical room is large and the refrigerant pipe would be complicated to run.

Do I need to insulate the house before installation?

Not necessarily, but it is very good to do it together. This is a question where many customers are mistaken in both directions. A heat pump does not work only in passive houses – we successfully install it even in 30-year-old family houses from the 70s. But a simple logic applies: the greater the heat loss, the higher the required pump power, the higher the initial investment and the higher the annual electricity consumption.

Practical example: a house from the 70s with unrenovated windows and no insulation of the perimeter walls may have heat losses of 15–18 kW at an outdoor temperature of -12 °C. This will require a pump with a power of 16+ kW and high-temperature heating (60–65 °C), which dramatically reduces efficiency. If you insulate the house and replace the windows, heat losses will drop to 8–10 kW, a smaller pump will be sufficient and you can operate at lower heating water temperatures – thus more efficiently.

Recommended order of steps: first an energy audit, then a decision on insulation, then selection and sizing of the heat pump. If you do everything at once (during renovation), you can also save on pump sizing.

What are the actual installation costs?

The total cost of installing an air-to-water heat pump for a family house in Slovakia in 2024 most often ranges from 8,000 – 18,000 € including VAT, depending on the power, manufacturer, installation complexity and required accessories. The cost breakdown is roughly as follows:

Outdoor + indoor unit (hydromodule): 5,000 – 12,000 €
DHW tank (if not part of the unit): 600 – 1,500 €
Accessories (expansion tank, safety valves, manometers, check valves, regulation): 300 – 800 €
Labor + refrigerant piping + electrical installation: 2,000 – 4,500 €

Accessories also include specialized materials such as Connecting set for models CALIBRA DUO and ATLAS DUO or Self-regulating heating cable for ITEC (2 m) to protect the piping of the monoblock unit from freezing. These seemingly minor items are technically important and their omission can cause operational problems or even damage to the equipment.

The return on investment depends on the previous heating method. When switching from direct electric heating (resistive heating), the payback period can be 5–7 years. When switching from gas, it ranges from 8–12 years at current energy prices – but this calculation changes quickly with energy price movements.

Do I need a special electrical circuit breaker or connection?

Yes, and this is a matter that is often overlooked during planning. Heat pumps are three-phase devices (400 V / three-phase power supply), not standard single-phase appliances. Before installation, you must:

Check whether your house has a three-phase connection (3 × 16 A or more)
Check the capacity of the main circuit breaker – a heat pump with a power of 8–12 kW can draw 6–10 A per phase during compressor start-up, plus other household appliances
Ensure a separate circuit with corresponding fuses and residual current devices
In the case of Smart metering systems, set up remote mass control (HDO) – most distributors offer a lower tariff for heat pumps

Electrical installation work must be carried out and handed over by a certified electrician. Without an electrical installation inspection report, your insurance company will not recognize damage in the event of a fault.

What is an expansion module and when do you need it?

An expansion module is an additional control hardware that extends the capabilities of the basic control system of a heat pump. You need it when your heating system is more complex than standard – for example, if you have multiple heating zones, mixed circuits, simultaneous floor and radiator heating control, or if you want to integrate external devices (e.g. solar collectors, heat recovery).

Specifically: Expansion module for ITEC models allows connecting additional heating circuits and expanding automation options. Without this module, you would have to add external controllers and zone valves with separate regulation – which is not only more expensive, but also a less elegant solution. A detailed analysis can be found in the article Expansion module for heat pump – when and why you need it.

Typical scenarios where you directly need an expansion module:

The house has floor heating in the ground floor and radiators on the upper floor (two different heating water temperatures)
You want to control the temperature separately in different zones (higher temperature in the bathroom, lower in the bedroom)
Integration with a heat recovery unit or photovoltaic inverter
Control of a mixed circuit – a Relay kit for mixed circuit can also help here, which converts a 3–10 V signal into a standard on/off signal for the pump

Can a heat pump be combined with solar panels or photovoltaics?

Yes, and it is becoming an increasingly popular combination. Each of these technologies has a different energy production profile, and their combination can complement each other very well.

Photovoltaics + heat pump: The most sensible combination in Slovakia. PV panels produce electricity during the day, and the heat pump consumes it for heating or hot water. Modern control systems (and some inverter-based heat pumps directly) allow for prioritized use of your own PV energy – when the sun is shining, the pump runs at full capacity and heats the storage tank, when not, it runs only as much as needed. A properly configured combination can reduce annual grid consumption by 40–60 %.

Solar collectors + heat pump: Solar collectors (thermal, not photovoltaic) preheat the water in the tank. The heat pump then heats it only to the desired temperature – saving energy. This combination is effective especially for DHW preparation in summer months, when collectors cover the entire demand and the pump is used almost not at all.

Hybrid systems: Some customers keep their original gas boiler as a backup and install a heat pump as the main source. The system switches automatically according to the outside temperature – in freezing weather it runs the boiler, in mild weather the heat pump. This is a bivalent connection, suitable especially for older houses with high-temperature heating systems.

How long does the installation take and what needs to be arranged?

The physical installation by a skilled and prepared team typically takes 2–4 days. However, the overall process from decision to start-up can take several weeks to months. Here is a realistic schedule:

Week 1–2: Energy audit, equipment selection, ordering
Week 3–5: Delivery lead time (usually 2–6 weeks depending on the manufacturer)
Week 5–6: Site preparation – concrete foundation for the outdoor unit, electrical circuit installation, possibly construction work (cutting a wall for refrigerant piping)
Week 6–7: Installation, refrigerant charging, regulation setup, start-up and test operation
After installation: Electrical inspection report, delivery of warranty documentation, registration with the distributor for the HDO tariff

More technical details about the installation process can be found in the article Heat pump installation – procedure, requirements and common mistakes, where we also cover the most common mistakes installers make and which customers then pay to have fixed by service technicians.

What is the lifespan of a heat pump and what maintenance does it require?

A properly installed and maintained heat pump has a lifespan of 15–25 years. The compressor, which is the most expensive and important part, lasts 15–20 years under normal load. Electrical components and pumps change sooner – usually after 8–12 years.

What should regular maintenance include (recommended once a year):

Check refrigerant pressure and possible topping up (only certified technicians for F-gases)
Cleaning the outdoor unit evaporator from dirt, leaves, dust
Check condensate drainage
Check electrical part – contacts, fuses, control module
Check expansion tank and heating water pressure
Flush the circulation water filter (if installed)
Firmware update of the controller (on modern units)

Some tasks can be handled by a skilled owner themselves – especially cleaning the outdoor unit, visual condensate check, checking pressure in the expansion tank or flushing the filter. What should not be done by yourself: work with refrigerant, checking electrical connections, replacing electronics. A detailed overview can be found in the article Maintenance and service of a heat pump – what you can do yourself and what you cannot.

What to do if the heat pump displays an error code?

The first reaction of most customers is panic and an immediate call to the service line. In practice, however, as much as 40 % of service calls are unnecessary, because the problem is trivial. Before calling a technician, check the following:

E01 / pressure drop: Check the pressure in the heating circuit on the pressure gauge. The correct pressure is usually 1.5–2.0 bar in a cold system. If it drops below 1 bar, add water using the filling valve (tap on the expansion tank).
Internal/external unit communication failure: Restart the system using the main power switch (not just turning it off from the display). If the error persists, check the network cable between the units.
High/low coolant temperature: Check whether the outdoor unit is not covered with snow or leaves. Clear the space around the evaporator.
Frost alarm: Check whether the self-regulating pipe protection cable is turned on (in case of a monoblock installation).

If the error code persists after basic inspection, it is time to call a service technician. Learn more about identifying faults in the article Common heat pump faults and how to recognize them.

Is a heat pump noisy? Can I place it near my neighbor's window?

Noise level of the outdoor unit is a legitimate concern, especially in residential areas with smaller plots. Modern heat pumps have noise levels in the range of 45–58 dB(A) at a distance of 1 meter, which corresponds to a quiet restaurant or a quiet street. At a distance of 3 meters, the level drops to 37–50 dB(A).

At night with reduced operation (nighttime damping), modern units can go below 40 dB(A) – the level of a quiet library. The law in Slovakia (MŽP decree) limits noise in residential areas to 50 dB(A) during the day and 40 dB(A) at night. With proper placement of the unit, there is no problem, but improper placement (right next to a neighbor's window or against a reflective wall) can lead to disputes.

Practical recommendations for placement:

Minimum distance from the property boundary: 1.5–2 m (for larger units ideally 3 m)
Do not direct the air discharge directly into a neighbor's or your own window
Anti-vibration pads under the base of the outdoor unit are a mandatory part of any proper installation
A sound barrier (fence, living hedge, small wall) can reduce perceived noise by 3–6 dB

Ground-source or air-source heat pump – how to decide?

This is a decision where there is no universal correct answer. Each type has its advantages and disadvantages:

Air-source: Cheaper installation (30–50 % cheaper), more flexible placement, easier maintenance, but lower SCOP in cold areas, noise from the outdoor unit, and reduced performance in freezing conditions.

Ground-source: Stable heat source throughout the year (ground temperature 8–12 °C even in winter), higher SCOP (3.5–5.0), quieter operation (only air ventilation in the machine room outside, if any), but significantly higher initial investment (ground collectors or drilling), need for a large plot of land or drilling permit.

In Slovakia, air-source systems are more common today because the price/performance ratio is better and installation is simpler. However, in higher altitudes or areas with long icy winters, ground-source can be more efficient. A detailed comparison of both types can be found in the article Air-source vs. ground-source heat pump – which one is more cost-effective.

Frequently asked questions (FAQ)

Can I install a heat pump myself without a professional?

Partially. Some preparatory work (foundation concrete, rough piping, space in the technical room) can be prepared by yourself. However, connecting the refrigerant circuit requires a certified technician authorized to handle F-gases – this is a legal requirement. The electrical connection must be handed over by an electrician with an inspection report. Installation without these documents will not be covered by the manufacturer's warranty and the insurance company will reject any claims.

Is any construction modification or permit required?

For most air-source heat pumps in single-family homes, no building permit or notification is required – as long as the outdoor unit is placed on the ground or on a wall and does not require special construction work. An exception is houses in heritage zones or protected natural areas, where an opinion from heritage or nature conservation authorities may be needed. For ground-source systems with boreholes, a hydrogeological assessment and a permit from the relevant environmental authority are always required.

How does a heat pump behave during a power outage?

During a power outage, the heat pump completely shuts down. It does not have its own backup power source – unlike, for example, a gas boiler with an atmospheric burner. If the safety of heat supply is critical for you (a house with children, flu season), it is worth considering either a bivalent system (gas backup) or a small backup power source (UPS) for the controller and circulation pumps for at least a few hours. After power is restored, the heat pump restarts automatically.

What is inverter technology and why is it important?

An inverter (variable speed compressor) allows the heat pump to smoothly adjust its output from 20 to 100 % according to current demand. Non-inverter pumps operate only in two modes: full power or off. Inverter units are quieter, have a higher SCOP (20–30 % lower electricity consumption), longer compressor lifespan (fewer starts = less wear), and more precise temperature control. Today, inverter technology is standard for every serious manufacturer in the mid to high price range.

Can I use a heat pump for cooling in summer?

Most modern air-source heat pumps support reverse cycle – that is, cooling. In summer, the device can cool the heating/cooling circuit to 7–18 °C and remove heat from the interior via floor heating (or cooling) or special fan-coil units. This is called active cooling. There is also passive (natural) cooling in ground-source systems – the ground is cooler than the interior in summer and cools directly without a compressor, using only a circulation pump, which is extremely energy efficient. If you plan to use cooling, inform your installer in advance – some components (e.g., fan-coils, condensate drainage) need to be designed from the start.

Are there grants or subsidies for heat pumps in Slovakia?

Yes, at the time of writing this article, there are several support schemes available. The most important one is Green for Home – a grant scheme by the Slovak Innovation and Energy Agency (SIEA), where you can receive a contribution of 1,000–4,000 € depending on the type and power of the heat pump. In addition, funding can be drawn from EU structural funds through municipalities for public buildings, or through loan products from the Slovak Guarantee and Development Bank for businesses. Conditions change, so always check the current status directly on the SIEA website or with your energy advisor.

Conclusion: a heat pump is not a miracle, but can be an excellent solution

A heat pump is a reliable, proven technology – if it is properly designed, installed, and operated. Problems usually do not come from the technology itself, but from underestimating the design phase: poor power sizing, unsuitable heating system, incorrect electrical connection, or insufficient accessories.

Therefore, selecting a heat pump is always a complex project – not just choosing a device from a catalog. If you are still in the thinking stage, we recommend starting with the article How to choose a heat pump – what to focus on before buying, where we cover the entire decision-making process from A to Z. And if you already have a specific project, feel free to look at our products in the category heat pumps – you will find there also complete accessories including all connecting and expansion components for a safe and proper installation.

Do you have a question about this topic?

Struggling to make a decision or dealing with a specific situation in your home? Write to us – we are happy to help.