Developing Asia has the world's fastest-growing rate of greenhouse gas emissions, with the leading driver being emissions from power generation. Reducing these emissions is paramount to ensuring a sustainable future while responding to the threat of climate change. This publication provides Asian Development Bank energy sector staff, consultants, and other interested readers with an understanding of key concepts and principles for estimating and reporting on the climate change impacts of energy projects. These guidelines provide more detail on estimating the emissions reductions attributable to energy efficiency and renewable energy projects.