This report has two objectives. One is to share the recognition of the state-of-the-art of current practices for heat pump systems among participating experts in the IEA EBC Annex 88 project ‘Evaluation and Demonstration of Actual Energy Efficiency of Heat Pump Systems in Buildings’, of which main activity will continue until June 2027. Another objective is to share the state-of-the-art with international, national, and industrial policymakers regarding the decarbonisation of buildings.

As many know, the heat pump is one of the most promising technologies for reducing energy use for space heating/cooling and domestic hot water and efficiently utilising renewable energies. However, inap-propriate design and the installation of heat pumps (e.g., capacity determined without sizing procedure, inappropriate operating temperatures, etc.) might negatively affect the energy consumption of this tech-nology and the system payback period might become longer than its lifetime.

Transparent technological information on the heat pump should be exchanged between HVAC design-ers/building owners and heat pump manufacturers. However, different viewpoints and technical approach-es have resulted in inconsistencies that represent an unresolved gap in product and building performance analyses that has limited the potential of the heat pump technology as an integrated part of efficient build-ings. It can be said the problem may not be purely technological but a sort of blind spot in existing stand-ards and regulations. Heat pump performance depends highly on the several parameters that define oper-ating conditions. It is difficult to identify and foresee their influences with simple tests and calculation methods. For example, energy efficiency of heat pumps under low partial load conditions (i.e., heat pumps operated inevitably much below their maximum capacity) is not appropriately represented by exist-ing testing standards and calculation methods for building energy codes.

The IEA EBC Annex 88 is a five-year R&D project between July 2022 and June 2027, and comprises the following five subtasks:
●　　　State-of-the-art for testing methods, monitoring methods and database, energy
　　　   calculation methods and design guidelines
●　　　Testing methods for heat pump products
●　　　Monitoring methods and database
●　　　Calculation methods of energy use by heat pump systems
●　　　Design guidelines for HVAC system designers