This paper presents the results obtained from laboratory testing of four liquid flat plate collectors. The collectors tested include a wavy fin collector, two flat plate heat pipe collectors, and a clip fin solar collector. The clip fin solar collector was tested, so as to compare this simple and inexpensive type of collector against the more costly wavy fin collector and the hat plate heat pipe collector. Using a similar basis of comparison, efficiency values have been formulated in order to compare the performance of the solar collectors. The experimental results show the clip fin solar collector to be promising, with experimental efficiencies approaching 86 per cent. Copyright (C) 2000 John Wiley & Sons, Ltd.