The goal of the study was to compare the efficiency of small hot water heat pumps using two different refrigerants, R410A and R32. The researchers set up heat pumps at a university to test how well they produced hot water. They found that the heat pump using R32 was more efficient, with a higher coefficient of performance (COP) compared to the one using R410A. This means that the heat pump with R32 could produce hot water using less energy, making it a better choice for saving energy.