In this study, an evaluation of thermo-hydraulic effect on offset finned absorber solar air heater has been investigated theoretically. A parametric study was done to investigate the effect of variation of system and operating parameters i.e. fin spacing (1 cm-5 cm), fin height (1.8 cm-5.8 cm), fluid mass flow rate (0.0139 kg/s to 0.083 kg/s) and insolation (750 W/m(2) and 950 W/m(2)) on the thermal and thermohydraulic (effective) efficiencies. Results indicate that the thermal efficiency increases continuously with increase in fluid mass flow rate, whereas thermohydraulic efficiency increases upto an inception value of fluid mass flow rate, attains a maximum and then decreases sharply for a given fin spacing and fin height. For higher value of the fluid temperature rise parameter, the effective efficiency values closely follow the thermal efficiency values. It is found that attaching offset fins below the absorber plate at lower fluid mass flow rate can lead to appreciable enhancement of the thermal and thermohydraulic efficiencies. (C) 2018 Elsevier Ltd. All rights reserved.