Installing both photovoltaics and solar collectors has positive environmental impact, as they reduce carbon emissions while providing external economic benefits. However, solar collectors have a higher conversion efficiency and lower lifecycle carbon emissions compared to photovoltaics. Since collectors and photovoltaic energy have different storage methods and purposes, the decision to install either photovoltaics or solar collectors on building rooftops should be based on the specific circumstances. In this paper, a detailed examination of the rooftop solar collectors in the graduate apartment building of Inner Mongolia University of Science and Technology is put forward various critical factors are analyzed, namely carbon emission, heat generation, energy savings, economic viability, and energy waste rate. Furthermore, the performance of three solar energy systems: the photovoltaic system, solar collector system, and photovoltaic coupled systems are assessed. To arrive at a comprehensive evaluation, the fuzzy comprehensive evaluation method are employed for these systems. Ultimately, our findings demonstrate that the collector system achieves the highest score in terms of performance and effectiveness. The factors influencing the performance of these three systems are discussed individually, leading to recommendations regarding whether to install photovoltaics or solar collectors on building rooftops.