It was September 2012, and the Energy for Development (E4D) team were returning from their first visit to Kitonyoni, an off-grid, rural market district in Makueni County, Kenya. An hour into the flight, they were discussing why so many rural electrification projects in developing countries tend to fail and fall into disrepair. Determined not to let this happen in Kitonyoni, they recognised their main challenge was to build a socially and economically sustainable model for rural electrification. This raised many questions, such as: How could they devise a service model which would generate sufficient revenues to sustain the system but remain affordable despite low and seasonal incomes? Which ownership or governance model would ensure community engagement; whilst at the same time recover the capital cost of installing a photovoltaic (PV) micro-grid? Finally, how could they reduce their capital costs by optimising the system design to meet local energy demands?