The ordinary on/off control method in solar heating systems which operates with fixed temperature differences is not the most appropriate solution to exploit the available solar energy. To increase the gathered solar energy, it was aimed at developing a new, energetically-based control algorithm. The block-oriented, physically-based model of the studied solar thermal system type was also developed and adopted to a particular installation at the campus of the Szent István University. Both the ordinary and the new control solutions were realized in the model. The tool of these works was the TRNSYS software. It is proved that the new control approach utilizes more solar energy in the studied case. It is highly expected that this advantage also applies to a great range of solar thermal systems. It should be mentioned that the new control algorithm requires an increased pumping time. As a conclusion it is suggested to consider the use of the new, energetically-based control method instead of the ordinary one since the collected solar energy is higher and the increment of the pumping cost can be decreased by effective pumps or photovoltaic support.