The article presents the data obtained as a result of an experiment to determine the effect of microwave radiation on the freezing rate of water in a heat pump installation are presented. (Research purpose) The research purpose is in experimentally evaluating the effect of microwave radiation on the speed of the water-ice phase transition to increase the efficiency of the heat pump unit by increasing the rate of water crystallization. (Materials and methods) The main criterion for conducting the experiment was the speed of the water-ice phase transition of ordinary water and water that passed through microwave radiation. The article presents an experimental installation for conducting experiments, consisting of a 90-liter freezer, a Danfoss TLES4F compressor with a cooling capacity of 91 Watts, a programmable Arduino controller with four connected sealed DS18B20 temperature sensors, a water tank made of food- grade plastic. The article presents the scheme of the experimental installation. The water was treated with microwave radiation for 12 seconds, the thickness of the water layer was 4-5 millimeters, and the power of the magnetron used was 750 Watts. (Results and discussion) There was conducted 20 experiments on obtaining thermal energy using the water-ice phase transition. Ten experiments with ordinary filtered water and ten experiments with water subjected to microwave radiation. (Conclusions) Water subjected to uniform microwave radiation cools to 0 degrees Celsius 23 minutes earlier than water that has passed only filtration, and performs a phase transition to a solid state 74 minutes faster. Microwave radiation can be used to increase the efficiency of a heat pump using the energy of the water-ice phase transition by accelerating the production of thermal energy from the heat carrier to the heat supply system.