Due to the observed increase of n-type panel C&I installations, the research on the performance of P-PERC and N-TOPCon modules in real world became an important topic from the practical point of view. This comparison was carried out by a third party institute CAS （Chinese Academy of Science） at a solar commercial rooftop system located in Ningbo, intending to help C&I system planners to choose photovoltaic modules taking into account the actual operating conditions. The result showed that the TOPCon bifacial module has higher energy yield performance, which is up to 8.9% higher compare to PERC modules, the majority of the contribution from lower degradation, optimized temperature coefficients, high bifaciality and advanced low-light performance.