This paper theoretically analyzes entropy generation, heat transfer enhancement capabilities and pressure drop of an absorbing medium with suspended nanoparticles (Al2O3, CuO, SiO2, TiO2 dispersed in water) inside a flat plate solar collector. Steady, laminar axial flow of a nanofluid is considered. These nanofluids considered have different nanoparticles volume fractions and volume flow rates in the range of 1-4% and 1-4 L/min, respectively. Based on the analytical results, the CuO nanofluid could reduce the entropy generation by 4.34% and enhance the heat transfer coefficient by 22.15% theoretically compared to water as an absorbing fluid. It also has a small penalty in the pumping power by 1.58%. (C) 2013 Elsevier B.V. All rights reserved.