In the UK, heating systems in the built environment consume a substantial proportion of its total energy and are responsible for about 25% of the total carbon emission. A similar pattern is also exhibited in many other European countries. Despite the enormous effort made over the last decades to improve the energy efficiency of these heating systems, a huge potential for further energy saving still persists. This paper investigates the potential for energy saving in heating systems that can be achieved through improving boiler controls. This investigation was carried out through surveys, simulation and experimental study. Through the surveys, typical boiler control schemes widely used in current practice were identified. The performance of some systems surveyed was monitored through the survey. The data obtained is used to demonstrate the problems associated with the control of boilers in heating systems. These typical control schemes identified through surveys were studied using a simulator that had been rigorously validated. An experiment was carried out to demonstrate how the overall performance of a heating system could be improved by using a better boiler controller. The result shows that improving boiler controls can lead to up to 20% of energy saving and a significant improvement in thermal comfort. (C) 2004 Elsevier B.V. All rights reserved.