SEI (System Efficiency Index)

Method and guidelines to establish System Efficiency Index for heat pumps and air conditioning systems


This project aims at defining a key performance indicator and developing a measurement and monitoring method for determining it on heat pump and air conditioning systems. This is to support energy optimization.

Traditionally COP (Coefficient of Performance) is used to define efficiency of heat pumps and air conditioning systems. However, high variance of COP with operating conditions makes it difficult to use for comparisons and difficult to communicate. Efforts are underway in several European countries to find better ways to define the efficiency of air conditioning and heat pump systems.

Within this project the concept System Efficiency Index (SEI) will be used for performance evaluation. SEI will be based on field measurements and provide a basis for monitoring, adjustment and identification of measures to optimize heat pump and air conditioning systems. SEI is based on the "old" concept of Carnot efficiency, i.e. comparing the measured COP with the COP of a process without losses which is operating under the same conditions. SEI varies much less than COP with changing temperatures and flows since changes in operating conditions are taken into account both in the measured and theoretically calculated value.

In the program Effsys + the Swedish Energy Agency has granted a project where SP, together with project partners, will develop method and guidelines for establishing of SEI for monitoring the energy efficiency of heat pumps and air conditioning.


The project is financed by the Swedish Energy Agency and participating project partners.

Time schedule

March 2012 - May 2014

Project partners

Clima Check AB (Sweden)
Kuhl Analyse (member of VDMA, Germany)
Ambient Control Ltd (UK)

Research staff at SP

Anna-Lena Lane, M.Sc. SP Energy Technology
Lina Eriksson, M.Sc. SP Energy Technology

Related project:

In a parallel project, funded by KYS -Kylbranschens samarbetsstiftelse, SP and project partners develop method and guidelines for establishing SEI on refrigeration systems for cooling and freezing applications.

Project partners are Clima Check AB, YIT, KV-företagen, Norpe, IOR and Kuhl Analyse.

SEI IOR Climacheck Kuhl Analyse SP Aleph Zero
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