The results of tests of 18 different small solar heating systems are presented. The systems are both test systems built by our Institute and marketed systems produced by Danish, Dutch, Swiss, Canadian and Norwegish manufacturers. The yearly thermal performance of the tested systems are determined under typical standard conditions. The tests showed that the heat storage is the most important component with regard to the thermal performance of the systems. Further, it is concluded that all the systems can be improved bychanging the design of the system.