Application of parabolic dish collector systems working in a range of low/medium temperatures is of great importance in industrial practice. In this work, a thermal efficiency analysis will be performed for different receivers such as a flat-plate receiver and a cavity receiver (with and without a glass cover). Most of the previous receivers analyses found in the literature have been performed for applications with high temperatures. Moreover, a detailed analysis including losses such as reradiation, natural and forced convection, and conduction, have been performed, developing new correlations for natural and forced convention. The obtained results are discussed in detail, obtaining a significant increasing of efficiency of the cavity receivers against the flat-plat receiver with much less working temperatures: up to 20% for the covered cavity receiver in comparison with the flat-plate receiver, with a temperature reduction at the receiver of more than 450 degrees C.