TERI Energy Data Directory Yearbook, or TEDDY, is an annual publication brought out by TERI since 1986. TEDDY is often used as a reference in other peer-reviewed books and journals for energy and environment-related data. It gives an annual overview of the developments in the energy supplying and consuming sectors as well as the environment sector. It also provides a review of the government policies that have implications for these sectors of the Indian economy. The book provides extensive data collated from the various government ministries, on the energy supply sectors including coal and lignite, oil and gas, power, and renewable energy sources and technologies; energy demand sectors, namely, agriculture, industry, transport and domestic sectors; along with information related to environment and climate change. Graphs and maps have been used extensively to explain facts, that makes the book an interesting read. Besides, detailed tables have been provided at the end of each chapter, making TEDDY a comprehensive data book. Each edition of TEDDY contains India’s commercial energy balances for the past four years that provide comprehensive information on energy flows within different sectors of the economy and how they have been changing over time. These energy balances and conversion factors are a valuable ready reckoner for anybody working on energy and related sectors. This is the 25th anniversary edition of the book and a number of refinements have been made in the content and presentation to reflect the changing needs of the readers. At the same time, care has been taken to ensure that continuity of information is preserved so that researchers can study the trends over time in the energy sector.