The aim of this book is to consolidate information from low temperature waste heat recovery demonstration sites. Apart from technical validation, the ReUseHeat project has generated knowledge about the urban waste heat potential in Europe, main stakeholders and different business aspects. Five stakeholder groups are targeted. These are urban waste heat owners, District Heating (DH) companies, policy makers, investors and customers. In the first chapter of the book, the concept of urban waste heat is introduced and the urban waste heat potential in Europe is presented. Thereafter (chapter two), information on business aspects is provided (stakeholders, value chain, risks, contracts and business model characteristics). Chapter three showcases the demonstrator concepts (waste heat recovery from data centre, hospital, metro and awareness creation about urban waste heat recovery) and performance data. Throughout the writing of the handbook, it was identified that it is important to compare the cost of different heating alternatives, to facilitate customer decision making. Therefore, a model was derived to compare costs of heating alternatives. It is presented in chapter four. Urban waste heat recovery is news. It is therefore important that stakeholders are made aware of the possibility to use the locally available heat and to start collaborating in new ways. To ensure as much stakeholder engagement as possible, the writing process of this book encompassed a six-month stakeholder involvement process. The stakeholder input is presented in chapter five. In chapter six, thoughts on the future development of district energy, policy implications and major learnings from the project are presented. This book was written within the ReUseHeat project. The work on the book was initiated after the first out of five years of activity to ensure that the consortium would be engaged in its development and to capture the knowledge generated on an ongoing basis. The final version of the book was ready and placed on the ReUseHeat webpage in September 2022. The project webpage remains in operation until 2024. The book not only exists in digital format. 600 copies were also printed and distributed to relevant stakeholders. All partners of the consortium have contributed to the writing of the book.