An experimental study was conducted to evaluate the thermal efficiency of a modified solar air heater. In the current design, air enters the collector through holes in front glass, passes through mesh layers, and exits at the backside of the air heater. A centrifugal fan was used to circulate air through the system. The design offers low construction costs and less solar radiation reflected from the collector. The modified collector was examined with various bed heights (30, 50, and 70 mm) and different mass flowrates of air varying from 0.011 kg/(s m2) to 0.043 kg/(s m2). The results showed that a counter flow collector with pierced cover had 5.6–9.7% higher efficiency than the single-pass one. The average efficiencies of the current design collector were found to be 55.2%, 44.6%, and 39.7% for the single-pass and 60.8%, 50.9% and 45.4% for the double-pass collector at 30, 50, and 70 mm bed heights and airflow rate of 0.043 kg/(s m2), respectively. The thermohydraulic efficiency, temperature difference, and perforated cover surface temperature were analyzed at each test and their effects on the system performance were evaluated. The highest amount of pressure drop through the collector was measured in the collector with a 70-mm bed height and a maximum air flowrate.