The fixed mirror solar concentrator (FMSC) possesses a geometry that can produce thermal energy in medium temperature range. Due to its static reflector, the FMSC has several advantages when compared to other designs, such as being one of the best adapted for integration onto building roofs. An optical ray-tracing analysis of its geometry was presented in a previous paper (Pujol Nadal and Martínez Moll, 2012, “Optical Analysis of the Fixed Mirror Solar Concentrator by Forward Ray-Tracing Procedure,” Trans ASME J. Solar Energy Eng., 134(3), pp. 031009-1-14). The optical results were obtained in function of three design parameters: the number of mirrors N, the ratio of focal length and reflector width F/W, and the intercept factor γ (in order to represent different receiver widths). In this communication, the integrated thermal output of the same parameter combinations has been determined in order to find optimal values of the design parameters at a working temperature of 200 °C. The results were obtained for three different climates and two orientations (North-South and East-West). The results show that FMSC can produce heat at 200 °C with an annual thermal efficiency of 39, 44, and 48%, dependent of the location considered (Munich, Palma de Mallorca, and Cairo). The best FMSC geometries in function of the design parameters are exhibited for medium range applications.