The steady state effect of vertical fins is assessed on a photovoltaic/thermal solar air heater having a double pass configuration in which fins are placed in the lower channel perpendicular to the direction of air flow. Air passes through the upper channel of the air heater and before passing in the opposite direction through the lower channel. The effects of design, climatic and operating parameters are evaluated on temperatures, efficiencies and other parameters. For fixed operating conditions, fins are observed to increase heat transfer area and rate, reduce cell temperature about 16^oC, and improve thermal and electrical efficiencies. Higher packing factors are advantageous as they increase electrical output per collector area and reduce cell temperature.