Heat Pumps Explained: Efficiency, Types, Savings, and How They Work

Heat pumps have become one of the most efficient and cost-effective heating systems for homes, apartments, and commercial buildings. Their popularity is on the rise due to high energy efficiency, reliable winter operation, and the ability not only to heat but also to cool your space. Unlike conventional heaters, which convert electricity directly into heat, a heat pump transfers energy already present in the environment-air, water, or ground-making heat pumps a leading choice for modern heating needs.

What Is a Heat Pump and Why Do You Need One?

A heat pump is a device that transfers heat from one medium to another: from outdoor air, ground, or water into your building. Unlike traditional electric heaters that generate heat directly, a heat pump harnesses the natural thermal energy of its surroundings. Even cold air contains enough heat to be "extracted" and delivered inside.

The main goal of a heat pump is to provide heating, hot water, and sometimes cooling with minimal energy use. It can deliver 3-5 times more heat than the electricity it consumes. This makes heat pumps an attractive alternative to gas boilers, especially where gas is unavailable or expensive. They're suitable for private homes, apartments with individual systems, greenhouses, offices, and commercial properties.

The Physics Behind Heat Pumps: Heat Transfer and the Refrigeration Cycle

Heat pumps work on the same physical principles as air conditioners and refrigerators: they don't create heat, they move it from a colder place to a warmer one. This is made possible by the circulation of a refrigerant-a substance that easily evaporates and condenses, absorbing and releasing heat during phase changes.

When the refrigerant evaporates at a low temperature, it absorbs heat from the environment-even if the air feels cold, there's enough energy for evaporation. Then the compressor compresses the gas, raising its temperature, and the hot refrigerant flows into a heat exchanger inside the building. There it condenses, releasing the accumulated heat into the heating system. Once cooled, the refrigerant passes through an expansion valve, lowering its pressure and preparing it for another cycle.

This process runs continuously. Since most of the energy comes from outside and electricity is mainly used to power the compressor, heat pumps are much more efficient than standard heaters.

Heat Pump Components: Compressor, Evaporator, Condenser, Expansion Valve

Every heat pump-regardless of type-has four key components that enable continuous heat transfer. These elements form a closed refrigerant circuit, allowing the system to 'collect' energy from outdoors and deliver it inside.

Compressor

The heart of the system. It compresses the gaseous refrigerant, sharply increasing its pressure and temperature. This makes the refrigerant hot enough to release heat indoors. The compressor is the main electricity consumer, so its efficiency largely determines the system's cost-effectiveness.

Evaporator

Located outside. Here, the cold refrigerant evaporates, absorbing heat from the air, soil, or water. Even at subzero temperatures, the evaporator can extract energy thanks to the refrigerant's low boiling point.

Condenser

Found indoors. The hot gas from the compressor enters, condenses, and releases heat to the heating or hot water system. After condensation, the refrigerant turns back into a liquid.

Expansion (Throttle) Valve

Lowers pressure and temperature of the liquid before it re-enters the evaporator, enabling the refrigerant to absorb heat again.

Together, these components maintain a continuous cycle where each stage utilizes the refrigerant's properties for efficient heat transfer. This is the foundation of a heat pump's high energy efficiency.

COP: Efficiency Coefficient and Why Heat Pumps Deliver More Than They Consume

The main advantage of heat pumps is that they deliver more heat to your home than the electricity they consume. This is measured by the Coefficient of Performance (COP). COP indicates how much thermal energy the device provides for each kilowatt of consumed electricity.

If the COP is 4, the heat pump supplies 4 kW of heat using just 1 kW of electricity-the remaining 3 kW come from the environment (air, ground, or water). As a result, heat pumps are much more economical than electric boilers, which have an efficiency of about 1 (they provide as much heat as they consume in electricity).

COP depends on outdoor temperature, compressor power, system type, and settings. The smaller the temperature difference between the heat source and your target indoor temperature, the higher the efficiency. That's why air-source heat pumps are especially effective in autumn and spring, while ground-source models perform well year-round.

COP is the key metric that makes heat pumps so attractive-they transfer heat rather than generating it, using the physics of refrigerant phase changes.

Types of Heat Pumps: Air-to-Air, Air-to-Water, and Ground-Source

Heat pumps are categorized by where they collect heat and how they deliver it. This impacts their efficiency, installation cost, and application.

Air-to-Air

The most common and affordable type. It works much like an air conditioner: heat is extracted from outdoor air and delivered inside as warm airflow. Simple to install, ideal for small homes and apartments. Efficiency drops in severe cold, but modern inverter models operate even at -20°C.

Air-to-Water

Extracts heat from the air but delivers it to a radiator or underfloor heating and domestic hot water system. Can work with radiators, boilers, or underfloor systems. Popular for private homes and can fully replace a gas boiler.

Ground-Source (Geothermal)

Uses the stable temperature of the soil. Collectors are placed horizontally or vertically in the ground. High efficiency even in winter, but installation is more costly and requires site preparation. Ideal for year-round operation.

Each type has its strengths: air-based systems are more affordable and easier to install, while ground-source pumps offer maximum stability and economy.

Inverter Heat Pumps: Boosting Winter Efficiency

Inverter heat pumps adjust compressor power smoothly, rather than switching on and off as traditional models do. This allows the system to adapt to outdoor temperature changes and the home's heating needs. The compressor runs at the minimum required speed, maintaining a stable indoor temperature without sudden load spikes.

This is especially important in winter. As outdoor temperatures drop, the heat pump must extract less energy from the environment, working more precisely and efficiently. The inverter lets the compressor increase its speed, keeping the COP high and preventing frequent stops that reduce efficiency.

Additionally, inverter control reduces frost buildup on the heat exchanger: the system more accurately controls refrigerant temperature and switches to defrost mode less often. This boosts performance at -10...-20°C and makes air-source heat pumps more reliable in cold climates.

How Much Electricity Does a Heat Pump Use?

A heat pump's consumption depends not on its rated power, but on how much heat your home needs at any given moment. On average, an air-source pump uses 3-5 times less electricity than an electric boiler, but actual consumption depends on several factors.

The main factor is outdoor temperature. The colder it is, the less heat is present in the air and the more work the compressor must do. In autumn and spring, consumption is minimal; in winter, it's higher, especially below -15°C.

Another factor is the heating circuit temperature. Underfloor heating needs a low supply temperature (30-40°C), so it's very economical. Radiators with high supply temperatures (55-70°C) increase the load and reduce system efficiency.

Insulation quality also matters-a well-insulated building needs less heat, meaning the heat pump can run in an economical mode most of the time. Inverter models further reduce consumption by adjusting output in real time.

On average, a home with a heat pump consumes less energy than with any other electric heating system, and with proper sizing, expenses can be 2-4 times lower.

Real Savings: When Are Heat Pumps Cheaper Than Gas or Electricity?

Heat pumps save money thanks to their high COP. For example, if a unit delivers 4 kW of heat per 1 kW of electricity, heating costs drop several times compared to direct electric heating. This is especially noticeable in homes that previously used convectors, electric boilers, or infrared systems.

Compared to gas, savings depend on local tariffs. In areas with high gas prices and affordable night-time electricity rates, heat pumps can be more cost-effective. They're most efficient in autumn and spring, when temperature differences are small, but with proper sizing and good insulation, can also keep winter running costs low.

Maximum savings are achieved in air-to-water systems with underfloor heating, which requires low supply temperatures. Here, COP remains high and costs are minimal. Ground-source pumps save even more thanks to stable soil temperatures-their efficiency barely drops in winter.

Overall, heat pumps are most advantageous where gas is unavailable, electric heating is too expensive, or homeowners want to reduce bills without sacrificing comfort.

Pros and Cons of Heat Pumps for Homes

Heat pumps are popular for their balance of efficiency and convenience, but like any technology, they have limitations. Knowing their strengths and weaknesses helps make the right choice and assess payback time.

Advantages:

• High efficiency (COP 3-5)-several times lower running costs than electric heating.
• Provides both heating and cooling-one system replaces a boiler and air conditioner.
• Safety-no gas, flames, or combustion products.
• Automation and stable temperatures-especially with inverter models.
• Ideal for underfloor heating-maximum cost savings.
• Low operating costs compared to most heat sources.

Disadvantages:

• Lower efficiency in severe cold for air-to-air and air-to-water models.
• Requires good home insulation for maximum savings.
• Higher upfront cost than electric boilers.
• Ground-source systems need major site work and space.

Despite the downsides, heat pumps remain one of the most cost-effective heating options, especially for year-round use and where electricity tariffs are favorable.

Conclusion

Heat pumps use simple, yet incredibly efficient, heat transfer physics: they don't generate energy, but extract it from the environment and deliver it to your home. Thanks to this, even household models can provide 3-5 times more heat than the electricity they consume, making them one of the most economical heating systems available.

Different types-air-to-air, air-to-water, and ground-source-suit varying needs and climates. Inverter compressors boost winter performance, lower consumption, and extend equipment life. With the right output, good insulation, and a low-temperature circuit (like underfloor heating), you'll achieve maximum savings and reliable year-round operation.

A heat pump is an investment that pays off through low operating costs, high energy efficiency, and versatility. It can fully replace traditional heating, offering comfort, safety, and lower electricity bills.