This joint report by the International Energy Agency (IEA) and the Nuclear Energy Agency (NEA) is the eighth in a series of studies on electricity generating costs. As policy makers work to ensure that the power supply is reliable, secure and affordable, while making it increasingly clean and sustainable in the context of the debate on climate change, it is becoming more crucial that they understand what determines the relative cost of electricity generation using fossil fuel, nuclear or renewable sources of energy. A wide range of fuels and technologies are presented in the report, including natural gas, coal, nuclear, hydro, solar, onshore and offshore wind, biomass and biogas, geothermal, and combined heat and power, drawing on a database from surveys of investment and operating costs that include a larger number of countries than previous editions.