The performance of two kinds of solar systems for space- and domestic hot water heating has been compared by computer simulations. One system is a conventional radiator-based heating system with collectors of 'ideal' collector coefficients. The second system is a low temperature heating system with solar collectors of moderate efficiency. The investigation shows that the difference in performance of the two systems is in the order of 1-6%. (C) 2002 Elsevier Science Ltd. All rights reserved.