Photovoltaic-thermal (PVT) hybrid collectors are co-generation components that convert solar energy into both electricity and heat and represent in principle one of the most efficient ways to use solar energy. The aim of the study presented in this paper is to assess the performance of this type of collector as part of a solar thermal system. First of all, the development and the test results of an experimental flat plate PVT collector are described. Then, in the second part, the performance of this hybrid collector being part of a solar thermal system in a building is determined and compared to that of systems operating with standard solar devices (i.e. solar thermal collector and PV panel), through simulations using TRNSYS. Comparisons according to various evaluation criteria were made assuming the same surface area and under the same climatic conditions. The results show that in configuration of limited available space for solar collector area, the use of efficient PVT collectors in the building envelop can be more advantageous than standard PV and solar thermal components, not only from an energetic point of view, but also considering the exergy and the primary energy saving.