In this paper, an energy analysis of a test laboratory for determination of the seasonal efficiency of a heat pump in a relevant environment is made. The research is part of the IRI 2 project entitled Development of an air-to-water heat pump with natural refrigerant and an advanced evaporator defrost system (KK.01.2.1.02.0132), co-financed by the European Regional Development Fund, ERDF. In order to achieve the project goals, system was designed on Faculty of mechanical engineering and naval architecture with an air-to-water heat pump for heating and cooling of total area of 200 m2 . The calculation of the design heat load of the subject was performed according to the standard HRN EN 12831, while the calculation of the design cooling load was performed according to the standard VDI 2078. The calculation was performed in the computer program AX3000. The design heat load for the heating season is 24,7 kW, while for the cooling season the design heat load is 11,3 kW. According to the calculation to the standard HRN EN 13790, the values of annual thermal energy for heating conditioned rooms in the amount of 12321 kWh were obtained, while the required annual thermal energy for cooling is 5460 kWh. The first prototypes of the Croatian heat pump manufacturers for low and medium temperature regimes application will be tested on the test line, and the seasonal efficiency of the heat pump will be determined. In the examined area, a ceiling heating and cooling system, as well as heating and cooling by means of a fan coil, ie a duct exchanger, are planned. Designed system is equipped with sophisticated measuring equipment to monitor all relevant parameters of the heat pump and control equipment with real-time data collection and contactless control. Furthermore, the design of the system envisages the possibility of testing the efficiency of commercial heat pumps available on the market in the relevant environment.