An approximate analytical model has been used to evaluate the optimum dimensions of a centralheating radiator. The radiator problem is divided into three one-dimensional fin problems and then the temperature distributions within the fins and heat-transfer rate from the radiator are obtained analytically. The optimum geometry maximizing the heat-transfer rate for a given radiator volume and the geometrical constraints associated with production techniques, and thermal constraints have been found. The effects of geometrical and thermal parameters on the radiator's performance are presented. (c) 2006 Elsevier Ltd. All rights reserved.