The role of policy instruments to promote the development and diffusion of energy efficient technologies has been repeatedly accentuated in the context of climate change and sustainable development. To better understand the impact of policy instruments and to provide insights into technology change, assessments of various kinds are needed. This study analyzes the introduction and development of energy efficient windows in Sweden and the policy incentives applied to support this process. The study focuses on the assessment of technology and market development of energy efficient windows in Sweden; and by applying the concept of learning, it assesses how conditions for learning-by-searching, learning-by-doing, learning-by-using and learning-by-interacting have been supported by different policies. The results show successful progress in technology development and an improvement in best available technology of Swedish windows from 1.8 W/m(2) K in the 1970s to 0.7 W/m(2) K in 2010; in the same time period the market share of energy efficient windows increased from 20% in 1970 (average U-value of 2.0 W/m(2) K) to 80-85% in 2010 (average U-value of 1.3-1.2 W/m(2) K). The assessment shows that various policy instruments have facilitated all four learning processes resulting in the acknowledged slow but successful development of energy efficient windows. (C) 2011 Elsevier Ltd. All rights reserved.