[en] In this thesis, I address four distinct - yet closely linked - research questions related to the adoption of solar energy technologies in East Africa, which will be summarized in the following section. Chapter 2 starts with an analysis of the history, status and prospects of solar energy markets in Kenya and Tanzania, and a comparison of both countries. Chapter 3 investigates the main determinants of solar home system (SHS) adoption in Kenya, and lighting fuel choices among Kenyan households. Chapter 4 examines the cost of (and potential for) large-scale, grid-connected solar PV adoption in Kenya, and Chapter 5 looks at the influence of financing costs on the economics of solar PV on a global level. With my research I therefore contribute to the policy debate surrounding the African energy challenge by looking at two countries in particular, namely Kenya and Tanzania. I have chosen this geographic focus deliberately, as both countries - while well-endowed with sunshine - at present use only very little solar energy. Thus, while the practical focus on East Africa in three of the four chapters implies that the wider African energy challenge is not tackled head on, many of the findings and conclusions from the study of Kenya and Tanzania are in my view transferable to other countries in Africa, and probably even beyond that continent. In conducting research on the solar energy markets of East Africa over the past five years (2009-2014) I have certainly learnt that this continent does not offer the easiest research environment, and a clear focus on a small set of countries and only one renewable energy technology has been very important. Rigorous, high-quality research requires good information, such as data and statistics, as well as appropriate methods; and while the latter are in good supply, the former are painfully lacking for many aspects of life in East Africa. This poses a major challenge for (quantitative) research and has greatly impacted what I could and could not do in my own work. The focus of this thesis is on solar energy technologies, as these have progressed most rapidly in recent years and as the (physical) potential to use the sun's energy is especially large in (East) Africa (Mandelli et al., 2014). Furthermore, solar energy technologies (particularly solar photovoltaics, or solar PV) have already been adopted on a larger scale in many developing countries in Africa and elsewhere (as well as developed countries, where they are being used to an even larger scale). For my research, this means that there were at least some data, history of market development, technology policies and evidence from previous research to work with. The overall contribution of my work is two-fold: First, I address specific research questions of relevance to both researchers and policymakers; and second, I do this in the context of a continent that is in many ways under-researched. According to Das et al. (2013) only around 3% of peer-reviewed papers in leading economics journals deal with sub-Saharan Africa, despite the fact that it accounts for some 12% of the global population (World Bank, 2010). In this context, the potential and future role of solar energy technologies for African development is one important aspect that is not yet fully understood. Helping to address this knowledge gap and advancing the knowledge frontier consequently seems of great relevance for informed policy decisions on both sustainable development and climate change mitigation.