This paper examines the key determinants that foster the adoption of photovoltaic (PV) power supply systems. The authors provide empirical evidence which suggest that 'government initiatives' and institutional 'finance' are important influencers of the decision to adopt PV power supply systems in developing countries. In order to diffuse PV technology it is also necessary to provide decision-makers with opportunities for direct and vicarious experience of PV systems through 'demonstration sites'. These factors have been ignored in earlier models of the innovation-decision process formulated by Rogers and the new innovation-decision framework proposed by Kaplan. Governments need to play a leadership role, and this coupled with the availability of Finance and Demonstration Sites will result in an increased interest leading to the adoption of PV technology in India. This research has led to the identification of variables such as the government initiatives, demonstration sites and finance, which are critical to the adoption of PV systems in developing countries like India. The research provided empirical evidence that is currently lacking in the area of adoption of PV technology in developing countries. (c) 2005 Elsevier Ltd. All rights reserved.