Heat pumps are considered efficient heating systems, but there is more to their technology than meets the eye. Terms such as COP, SCOP and JAZ reappear again and again — but what do they actually mean? Anyone who owns or plans a heat pump should know the most important key figures and technical terms. In this article, you will find the most important terms and their meaning.

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What is COP (Coefficient of Performance)?

The COP (Coefficient of Performance) indicates the ratio of generated heating power to absorbed electrical power at a specific moment. It is measured under laboratory conditions and shows how efficiently a heat pump works under ideal conditions.

The value depends on several factors, including Heat source temperature, the flow temperature And the Compressor efficiencys. A high COP means an efficient heat pump with low power consumption.

Since the COP is only a snapshot, it does not provide any information about year-round efficiency. For a realistic evaluation of efficiency, the SCOP or JAZ is more meaningful.

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How do you calculate the COP value?

The COP value is calculated by dividing the heating power by the electric drive power. The formula is:

COP = heating output (kWh)/electric drive power (kWh)

The electric drive power describes the amount of electricity used for this in kWh.

A higher COP means a more efficient heat pump, as more heat is generated with less electricity. The COP is determined under standardized laboratory conditions in accordance with EN 14511 and represents a snapshot. For a year-round efficiency assessment, the SCOP or JAZ is more meaningful.

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What is a good COP value?

A good COP value is usually between 3.1 and 5.1, depending on the type of heat pump and operating conditions. Heat pumps with a COP below 2 are considered uneconomical.

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What is SCOP (Seasonal Coefficient of Performance)?

The SCOP (Seasonal Coefficient of Performance) gives the average COP over an entire year and is therefore a more realistic efficiency indicator. In contrast to the COP, the SCOP takes into account seasonal fluctuations such as winter, summer and transition periods. It shows how efficiently a heat pump works under real operating conditions.

A high SCOP means a better annual performance figure and lower electricity costs. The calculation is based on standardized climate zones and heating load profiles. The SCOP is therefore an important value for comparing different heat pump models.

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How do you calculate the SCOP value?

The SCOP value is calculated by dividing the heating energy generated over a year by the electrical energy expended for it. The formula is:

SCOP = heating capacity (kWh)/electric drive power (kWh)

The calculation takes into account the varying heat demand and the changing outdoor temperatures in different seasons. Standardised climate zones and operating points are defined for this purpose. Depending on location and heating requirements, the actual SCOP may differ from laboratory measurements. A high SCOP value means a more efficient heat pump with lower operating costs.

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What is a good SCOP score?

A good SCOP score is at least 3.5 to 5.0, depending on the type of heat pump and climatic conditions. Heat pumps with a SCOP below 3.0 are considered inefficient and lead to higher electricity costs.

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What is JAZ (annual performance figure)?

The JAZ (annual performance figure) indicates the actual efficiency achieved by a heat pump in practical operation over one year. It is calculated on the basis of real electricity consumption and the actual heating output generated. In contrast to SCOP, which is based on standardized climate data, JAZ takes into account all individual influences such as building insulation, heating behavior and regional weather conditions.

A high JAZ value means an efficient heat pump with low electricity costs. The JAZ can be improved through good planning, a low flow temperature and optimal heat pump control.

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Which factors influence JAZ?

The JAZ (annual performance factor) is influenced by several factors that have a direct effect on the efficiency of the heat pump in real operation.

• flow temperature: The lower the flow temperature, the more efficiently the heat pump works. Around 35°C is optimal, which is why surface heating systems such as floor, wall or ceiling heating systems are particularly suitable. High flow temperatures increase power consumption and reduce efficiency.
• heat source: The temperature difference between heat source and flow temperature influences JAZ. Water/water heat pumps have the best values, as groundwater offers high temperatures all year round. Air/water heat pumps perform worse because the outside air cools down significantly in winter.
• building insulation: Good insulation reduces heat consumption and improves JAZ, as the heat pump needs to heat less.
• outdoor temperature: In colder regions, the JAZ is usually lower because the heat pump requires more energy to compensate for the higher temperature difference between heat source and flow temperature.
• usage behavior: Frequent ventilation, overheated rooms or uneven heating of individual rooms increase heat demand and lower JAZ. Weather-controlled heating control helps to optimize efficiency.

For a better overview:

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How do you calculate JAZ?

The JAZ (annual performance figure) is calculated by dividing the heating energy generated in the year by the electrical energy used for it. The formula is:

JAZ = annual heating capacity/annual electricity consumption

• Annual heating output: The total amount of heat generated in the year in kilowatt hours (kWh).
• Annual power consumption: The total electrical energy required for this in kilowatt hours (kWh).

An example:

• A heat pump produces per year 15,000 kWh Heat for heating and hot water.
• The power consumption of the heat pump is 4,000 kWh.
• The JAZ is: 15,000 kWh/4,000 kWh = 3.75.

A higher JAZ means a more efficient heat pump with lower electricity costs. It can be improved by a low flow temperature, good thermal insulation and optimal heating control.

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What are good JAZ scores?

Depending on the type of heat pump and operating conditions, good JAZ values are between 3.5 and 6.0. Heat pumps with a JAZ below 3.0 are considered inefficient.

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Other important terms relating to heat pumps

defrosting

At low outdoor temperatures, moisture from the air can settle on the evaporator of an air heat pump and freeze. To ensure that efficiency does not fall, the heat pump defrosts automatically through a defrost function. The required heat can be extracted from the heating circuit or from a buffer tank.

Work equipment

The working medium in a heat pump is refrigerants. It absorbs heat, evaporates and then releases the stored energy again before being liquefied again. Since the circuit is closed, the refrigerant is not consumed, but only changes between aggregate states.

Direct evaporation

In heat pumps with direct evaporation, the refrigerant evaporates directly in a geothermal collector, eliminating the need for an additional heat exchanger and a brine pump. As a result, the system works more efficiently, requires less maintenance and is reliable.

efficiency

The efficiency of a heat pump is determined by various indicators such as JAZ, COP and SCOP described. High efficiency means that less electricity is required for the same heating output.

EHPA seal of approval

The EHPA seal of approval (European Heat Pump Association) confirms the high quality of a heat pump. It is only awarded if certain technical, planning and service-related requirements are met.

electric heating rod

An electric heating element is an additional heater that is used in heat pump systems when the heat pump is unable to provide sufficient heat at extremely low temperatures. It works with electricity and serves as an emergency solution for particularly cold days.

ETAS value

The ETAS value indicates the seasonal space heating efficiency of a heat pump. It describes how much primary energy is required to generate one kilowatt hour of heat. The value is calculated from the SCOP number by 2.5 is shared.

expansion valve

The expansion valve regulates the pressure and quantity of refrigerant in the heat pump refrigeration circuit. It ensures that the refrigerant regenerates after heat has been released and can absorb heat again.

heating curve

The heating curve defines how the flow temperature of the heat pump changes as a function of the outside temperature. A well-adjusted heating curve ensures efficient heat generation and prevents unnecessarily high flow temperatures, which increase power consumption.

heating capacity

The heating capacity of a heat pump is expressed in kilowatts (kW) and describes how much heat the system can provide under certain conditions. This value depends on the source temperature and the set flow temperature.

heating demand

The heating demand indicates how much heat energy is required per year to heat a building and provide hot water. It depends on the size of the building, insulation and user behavior.

inverter technology

Heat pumps with inverter technology continuously adjust their output to current heating requirements. As a result, they work more efficiently than devices with on-off operation, reduce electricity costs and extend the life of the components.

supercharger

The compressor compresses the gaseous refrigerant, causing its temperature to rise. At the same time, it transports the refrigerant through the closed circuit of the heat pump.

condenser

The condenser is a heat exchanger in which the gaseous refrigerant is cooled and liquefied. In doing so, it transfers the stored heat to the heating system.

buffer tank

A buffer tank is a heat accumulator that absorbs excess heat and releases it back to the heating system when required. It ensures uniform heat output, reduces the need to switch the heat pump on and off frequently and improves its efficiency. A buffer tank is particularly advantageous in systems with radiators or during blackout periods.

return temperature

The return temperature indicates the temperature at which the heating water flows back to the heat pump after heat has been released into underfloor heating, wall heating or radiator.

brine

Sole is a mixture of water and antifreeze which is used as a heat transfer medium in brine/water heat pumps. It absorbs heat from the ground and transports it to the evaporator.

Blackout periods

Blackout periods are periods during which network operators can temporarily interrupt the power supply to a heat pump. This serves to ensure grid stability and usually applies to discounted heat pump tariffs. For this period, the heat pump requires sufficient heat storage, e.g. in the form of a buffer tank, so that it can maintain heating operation.

spread

The spread describes the temperature difference between flow temperature and return temperature in the heating circuit. A small spread improves the efficiency of the heat pump.

circulating pump

The circulation pump ensures that the heating water or brine liquid is transported within the heat pump system. It works electrically and influences the energy consumption of the system.

evaporator

The evaporator is a heat exchanger that absorbs environmental heat from air, water or soil. In the process, the refrigerant evaporates and starts the heat pump cycle.

evaporation temperature

The evaporation temperature is the temperature at which the refrigerant changes its aggregate state from liquid to gaseous. This process takes place in the evaporator as the refrigerant absorbs ambient heat.

Compactor

The compressor is another word for the compressor. It increases the pressure and temperature of the refrigerant so that the heat can be transferred to the heating system.

flow temperature

The flow temperature indicates the temperature at which the heating water is directed into the floor heating, wall heating or radiator. Low flow temperatures improve the efficiency of the heat pump.

heat source

The heat source is the medium from which the heat pump extracts energy. Depending on the type of heat pump, this can be air, soil or water. The efficiency of the heat pump depends heavily on the temperature of the heat source. Groundwater offers the most consistent temperatures, while air heat pumps must operate with highly fluctuating temperatures.

heat exchanger

A heat exchanger transfers heat from one medium to another without the two media mixing. There are various heat exchangers in a heat pump, including the evaporator and the condenser.

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