as boilers and air conditioners. The textbook contains chapters about the fundamental idea, energy markets, customer demands, load variations, supply, environmental impact, distribution, substations, system functioning, economics, planning, historical development, current and future use, organisation, and information sources concerning the flows of heat and cold in district heating and cooling systems. District heating and cooling is an interdisciplinary technology containing elements from many general technologies and methodologies such as combustion, heat transfer, piping, marketing, billing etc. Our mission has been to provide basic introductory knowledge about aspects typical of district heating and cooling, which is very vital for a basic understanding of, or very unique for, this niche technology. We have a rather broad range of readers in mind: District heating engineers, university students of engineering, and employees at district heating companies in general. We will be happy if urban planners, economists, policymakers and others interested in the topic will find that this book provides tangible and useful information about district heating and cooling.