State-of-the-art and emerging testing methodologies for performance evaluation of air conditioners and heat pumps

Renewable and Sustainable Energy Reviews, vol. 244, pp. 117391

Abstract

Modern test methods for air conditioners and heat pumps must reconcile two competing demands: accurately reflecting real operating behavior and ensuring practicality, repeatability, and interlaboratory comparability. Conventional fixed-speed, steady-state rating procedures fall short of this objective, as they exclude control dynamics and interactions with buildings and distribution systems, thereby limiting their representativeness of in-use performance. This review critically examines the limitations of current testing standards and synthesizes recent research and technical advances aimed at improving performance characterization and seasonal efficiency assessment. Emphasis is placed on load-based testing methodologies, emulator-based approaches, and hardware-in-the-loop (“field test in the lab”) concepts, which enable active-control operation under reproducible yet realistic conditions. Evidence from laboratory demonstrations, interlaboratory comparisons, and emerging standardization efforts is consolidated to assess the technical maturity, robustness, and scalability of these methods. The discussion also reflects ongoing international initiatives, including International Energy Agency Annex 88, “Evaluation and Demonstration of Actual Energy Efficiency of Heat Pump Systems in Buildings,” and the International Organization for Standardization Informal Meeting on “Load-based Test Methods.” Based on the reviewed methods, the paper identifies pathways toward next-generation testing frameworks that better recognize advanced system architectures and control strategies, support evidence-based policy and standardization, and provide consumers with performance metrics that more closely align with real-world energy outcomes.

Authors 15

1. Niccolò Giannetti corresponding

   Waseda University

   Affiliation as printed

   Sustainable Energy & Environmental Society Open Innovation Research Organization, Institute for Energy and Environmental System, Waseda University, Tokyo, 169-8050, Japan

2. Christian Vering Aachen Institute for Energy Efficient Buildings and Indoor Climate

   RWTH Aachen University

   Affiliation as printed

   Institute for Energy Efficient Buildings and Indoor Climate, RWTH Aachen University, 52074, Aachen, Germany

3. Parveen Dhillon

   National Laboratory of the Rockies

   Affiliation as printed

   National Laboratory of the Rockies, Golden, CO, 80401, USA

4. James E. Braun

   Purdue University West Lafayette

   Affiliation as printed

   Ray W. Herrick Laboratories, School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907-2099, USA

5. André Wachau

   Federal Institute For Materials Research and Testing

   Affiliation as printed

   Section Ecodesign and Energy Labelling, Federal Institute for Materials Research and Testing (BAM), Berlin, Germany

6. Hamza Salih Erden

   Federal Institute For Materials Research and Testing · Istanbul Technical University

   Affiliation as printed

   Department of Computational Science and Engineering, Informatics Institute, Istanbul Technical University, Istanbul, Türkiye

   Section Ecodesign and Energy Labelling, Federal Institute for Materials Research and Testing (BAM), Berlin, Germany

7. Napoleon Enteria

   Mindanao State University – Iligan Institute of Technology

   Affiliation as printed

   Department of Mechanical Engineering and Technology, College of Engineering, Mindanao State University – Iligan Institute of Technology, Tibanga, Iligan City, 9200, Philippines

8. Jeremy Sager

   Natural Resources Canada

   Affiliation as printed

   Natural Resources Canada, CanmetENERGY-Otawa, Canada

9. Bruce Harley
   Affiliation as printed

   Bruce Harley Energy Consulting, LLC, Stamford, VT, 05352, USA

10. Yash Shukla

    CEPT University

    Affiliation as printed

    CEPT University, Kasturbhai Lalbhai Campus, University Rd, Navrangpura, Ahmedabad, Gujarat, 380009, India

11. Arnas Lubis

    University of Indonesia

    Affiliation as printed

    Department of Mechanical Engineering, Faculty of Engineering, University of Indonesia, Depok, 16424, Indonesia

12. Stephan Göbel Aachen Institute for Energy Efficient Buildings and Indoor Climate

    RWTH Aachen University

    Affiliation as printed

    Institute for Energy Efficient Buildings and Indoor Climate, RWTH Aachen University, 52074, Aachen, Germany

13. Dirk Müller Aachen Institute for Energy Efficient Buildings and Indoor Climate

    RWTH Aachen University

    Affiliation as printed

    Institute for Energy Efficient Buildings and Indoor Climate, RWTH Aachen University, 52074, Aachen, Germany

14. Takao Sawachi

    The Building Center of Japan

    Affiliation as printed

    The Building Center of Japan, Chiyoda-ku, Tokyo, Japan

15. Kiyoshi Saito

    Waseda University

    Affiliation as printed

    Department of Applied Mechanics and Aerospace Engineering, Waseda University, Tokyo, 169-8555, Japan