A computational study on active and passive evacuated tube solar collector system is examined in this paper. The paper gives us an understanding of the performance of the ETC system under natural flow as well as forced circulation. Major parameters for useful solar thermal energy gain by evacuated tube solar collector are tilt angle, mass flow rate and specific heat capacity of working fluid. To make sure that the system receives maximum useful heat gain, the optimum mass flow rate has been analyzed using ANSYS Fluent CFD. Thermal efficiency of active evacuated tube solar collector at optimum mass flow rate is compared with thermal efficiency of passive evacuated tube solar collector. It is observed from the numerical modeling of the evacuated tube solar collector that passive system is more efficient than active system. © Springer Nature Singapore Pte Ltd. 2019.