Abstract In the present paper, the performance analysis of finned absorber solar air heater has been investigated analytically. The fluid channel is formed by two transversely positioned wavy fins attached on the absorber plate with bottom side thermally insulated and the top surface of absorber subjected to uniform heat flux. The expression for collector efficiency factor of such collector has been developed. Effects of mass flow rates and fin spacings on the thermal performance have been presented and the results are compared with plain solar air heater. Further, the thermohydraulic performance parameter called ‘effective efficiency’ has been employed and presented to express the net useful thermal energy gain, taking into account the equivalent thermal energy required to produce the work energy necessary to overcome the additional friction or hydraulic losses as a result of extended surfaces on the absorber plate. The mathematical model provides reasonable predictions of the performance of wavy fin solar air heater and it can be useful in designing such types of solar air heater.