Improve the ErP class of a compound system with heating controllers

Improve the ErP class of a compound system with heating controllers

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Significance / Relevance

Climate change and energy efficiency are on everyone’s lips. Private energy demand plays an important role in achieving climate goals. A good quarter of the total final energy consumption within the EU is accounted for by private households. Of this “final energy consumption”, in turn, more than 63% is accounted for by space heating.

“In the EU, the main use of energy by households is for heating their homes.“

For this reason, the EU Commission created the Europe-wide ERP Directive (long: “Energy related Products Directive”).

Its goal:

  • increase energy efficiency.
  • create awareness for energy efficiency among consumers.
  • provide orientation for consumers by making energy efficiency comparable.

Product label / composite label

In order to achieve the goals of the ERP Directive and to make energy efficiency an easily comparable criterion in purchasing decisions, products that fall under the ERP Directive must be labelled with an energy efficiency label (also called an “ERP label”).

A distinction is made between a product label and a composite label (or package label).


Product label:

  • For stand-alone products
  • Issued by the manufacturer

Composite label:

  • For systems consisting of several components
    associated heating components in the package label: temperature controllers, solar systems with solar-powered hot water tanks, auxiliary heaters.
  • The composite label for complete systems is issued by the manufacturer or, in the case of assembled components, by the installer (e.g. with the help of the calculator at
  • Displays two energy efficiency classes
    1) (Left side) Efficiency from the product label
    2) (Right side) Energy efficiency of the system
  • Energy efficiency of the system is determined by the sum of the individual energy efficiencies and then a new classification is made by scale

Energy efficiency class

The most important part of the ErP label is the division into energy efficiency classes. Here, products are currently classified on a scale from G to A++. From March 2021, however, the “plus” classes are to gradually disappear and there will only be classes A to G.

The classification into the respective class on the scale is made on the basis of the so-called energy efficiency ratio.

This is defined thus:

“Seasonal space heating energy efficiency” (ηs) means the quotient of […] the covered space heating demand in a given heating period and the annual energy consumption to cover this demand in %.”


Determine the efficiency of a controller of the temperature class

Controllers are an important part of a compound system and increase the overall efficiency of a system. This is taken into account in the composite label by adding the energy efficiency of the controller.

The efficiency index of the controller is taken from the appropriate temperature controller class. A classification is made on the basis of criteria that must be fulfilled in order to achieve this class.

Note: A higher class does not directly mean higher energy efficiency. If you look closely, you will notice that class 2 has a higher efficiency than class 3. The same applies to classes 6 and 7.

Once the appropriate class for the controller has been found, the corresponding energy efficiency can be taken from the table and included in the composite label.

Examples of temperature controller classes

The following overview illustrates the classification of temperature controllers based on these criteria and gives concrete examples for the individual classes.

Class 1:
Stand-alone bi-metal thermostat
Ex.: RC21

Class 2:
Weather-compensated heating circuit with modulating energy demand. Ex.: MHCC

Class 3:
Weather-compensated heating circuit with on/off energy demand. Ex.: LHCC

Class 4:
Room-guided energy request
Ex: °CALEON thermostat

Class 5:
Room-guided (1) control with modulating energy demand (2).

Class 6:
Room (1) and weather-compensated (2) control with modulating energy demand (3). Ex.: LHCC + °CALEON + burner

Class 7:
Room (1) and weather-compensated (2) control with on/off energy demand (3). Ex.: LHCC + °CALEON + burner

Class 8:
Multi-zone control with modulating energy demand. Example: °CALEONbox with 0-10V boiler control + °CALEON + room sensors

Integration of the controller class into the composite label

Once the appropriate class for the controller has been found, the corresponding energy efficiency can be taken from the table and included in the composite label. To calculate the overall efficiency of a combined system, the energy efficiency figures of the individual components are added together. The following graphic illustrates the procedure.

Finally, here is a result from a survey conducted by the German Environmental Protection Agency (Umweltbund) on why reaching a higher level in the ERP label can be worthwhile:

In 84% of cases, the energy label influences the purchase decision .

Source: * “Environmental Awareness in Germany 2014”, representative population survey, published by the Federal Environment Ministry and the Federal Environment Agency.


Controllers play a decisive role in the energy efficiency of heating systems. The ERP label also takes this into account. In the composite label, the “energy efficiency” figure of the temperature controller is added. Thus, not only the system itself but also the ERP class can benefit from the use of a suitable controller.

Marvin Alexander Gellenthin

About the Author

After completing a master’s degree in industrial engineering, Marvin Gellenthin first gained experience in mechanical engineering and is now dedicated to the automation of HVAC systems.

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