Solar electricity produced by photovoltaic solar cells is one of the most promising options yet identified for sustainably providing the world's future energy requirements. Although the technology has, in the past, been based on the same silicon wafers as used in microelectronics, a transition is in progress to a second generation of a potentially much lower-cost thin-film technology. Cost reductions from both increased manufacturing volume and such improved technology are expected to continue to drive down cell prices over the coming two decades to a level where the cells can provide competitively priced electricity on a large scale. The subsidised, urban residential rooftop application of photovoltaics is expected to provide the major application of the coming decade and to provide the market growth needed to reduce prices. Large centralised solar photovoltaic power stations able to provide low-cost electricity on a large scale would become increasingly attractive approaching 2020.