It is widely believed that energy efficiency improvement is one of the most interesting options to limit the emissions of the greenhouse gas carbon dioxide. But, it also has become clear that it is not easy to stimulate companies to adopt measures in this area. Therefore, a main question is: how can governments implement effective policies to stimulate energy-efficiency improvement? The Netherlands and some neighbouring countries in Europe have implemented a variety of policy instruments since 1990. These include investment subsidies, voluntary agreements on energy-efficiency, direct regulation and taxes. How effective are these measures? This book presents improved theoretical insight in the investment behaviour of firms, and moreover it provides a wealth of empirical results on the effectiveness of policy instruments.