The analysis of the behavior of thermal storage load systems under typical solar conditions may be realized in the laboratory if a heat source is available that behaves like a predifined solar collector. For this purpose a collector hardware simulator (CHS) was built. This CHS allows repetitive experiments with solar storage load systems under variable conditions of temperature and power. The influences of different radiation time patterns, of the collector parameters and of the collector size on the performance of the coupled storage-load system may be studied easily in ＇＇quasi-solar＇＇ experiments. The description of the CHS includes the analysis of the dynamic behavior of, both, solar collectors and the CHS in the time domain as well as in the frequency domain. The governing differential equations are formulated, and the transfer functions that are obtained by means of Laplace transforms are presented. These transfer functions allow a clear assessment as to which collectors under which conditions can be simulated by a given CHS.