This thesis describes utilisation of test reference year for design and evaluation of solar thermal system. The evaluation was performed on a solar thermal system of a single-family house in Rapotice, Czechia. Long-term monitoring of the system as well as indoor and outdoor climate were performed there. Measured data were compared with test reference year and data in Meteonorm database. Selected boundary conditions of the solar thermal system were compared with numerical simulations in Polysun. The results of the comparison were statistically analysed. Results of the simulations utilizing test reference year were closer to the on-site measurements than dates from Meteonorm. Therefore it could be concluded that test reference year is the best database of climate data for design of solar thermal system in Czechia.