Unbundling power generation, transmission, and distribution is not an end itself, but rather a means to achieve better performance. The key objective of the analytical framework of this paper is to explore the links between alternative market structures and performance (in terms of access, price, quality, and technical and financial performance). The results are crucial for providing policy advice, by offering alternative options to policy makers based on the lessons learned from the taxonomy of different market structures, tailored to different national contexts. The analysis is based on unique data, including a panel of 22 countries for the period beginning in 1989 and extending through 2009. The results of the analysis carried out for this study confirm the following conclusions for policy guidance on power market restructuring for developing countries. First, unbundling delivers results in terms of several performance indicators when used as an entry point to implement broader reforms, particularly introducing a sound regulatory framework, reducing the degree of concentration of the generation and distribution segments of the market by attracting public and private players and private sector participation. Second, there seems to be a credible empirical basis for selecting a threshold power system size and per capita income level below which unbundling of the power supply chain is not expected to be worthwhile. Finally, partial forms of vertical unbundling do not appear to drive improvements, probably because the owner was able to continue exercising control over the affairs of the sector and hinder the development of competitive pressure within the power market.