This is an introduction to Central Utility Systems concepts, theories, components and some operations practices. In addition to introducing plant operators to the very basic level of knowledge needed to understand the plant, the best fit for this book may be for those who have some duties in and around the plant and could benefit from some of the basic terms and definitions supplied here. The book focuses on District Energy Systems, but applies to virtually any boiler or steam plant and the systems they use to operate safely and efficiently. The strongest value that this book will bring is a common language as every reader will have the ability to understand the terms and phrases used in and about the plant.