The purpose of this paper is to assess the effects, the cost efficiency, and the goal achievement of policy instruments aimed for the development and deployment of wind power in Sweden during the period 1975 to 2000. The paper presents an empirical example of a socio-technical system-based approach for impact assessment, in which changes in the wind power system are described and analysed with respect to technology development, cost development and actors' involvement. The results show that the policy instruments were not designed to have a broad, system-oriented perspective but targeted and included restricted technology concepts-i.e. large, two-bladed turbines-and limited involvement of actors. The assessment shows that early inflexible steering of technology and market development, together with a lack of comprehensive, long-term strategy, lack of continuity in policy interventions and weak combinations of policy programmes and measures have contributed to a very limited wind power development in Sweden. A rough cost efficiency analysis reveals that Sweden has much less wind power installed in relation to expenditures on various support than Germany and Spain. The Swedish policy instruments did, however, achieve the Government's goals to increase wind energy production. (c) 2004 Elsevier Ltd. All rights reserved.