Most solar collectors employ a transparent cover plate often made of glass. These materials reflect around 8% of the incident solar radiation, which leads to the reduction in the collector heat output. The use of an antireflection coating could therefore improve the performance of such a system by increasing the transmitted energy through the glass cover. Recently, a silica low-reflection coating via a dip-coating process has been developed. The refractive index of the thin film is well controlled. The exact value of the film refractive index that leads to a minimum of reflection on the surface of the glass cover call be achieved. A comparison has been made between an uncoated flat-plate solar collector glass cover and one with a porous sol-gel antireflection coating. Using the porous sol-gel coating with the index of refraction of n = 1.23 on the glass cover of the solar collector increases the useful energy by a factor of approximately 1.05.