The Central Solar Water Heating Systems Design Guide is the first attempt to develop recommendations on optimal and reliable configurations of solar water heating systems in different climates along with design specifications, planning principles, and guidelines for such systems that serve building clusters with significant domestic hot water (DHW) needs (e.g., barracks, dining facilities, Child Development Center [CDC], Gyms) that operate in combination with central heating systems. Note that, throughout the industry, the terms "district heating system" and "central heating system" are commonly used interchangeably. For the purposes of this document, the term "Central Solar Hot Water System" is used to denote systems that serve clusters of buildings from a large centralized solar thermal field(s) (in contrast with small size solar thermal systems that serve standalone buildings). The guidelines are complemented by numerous case studies of successfully implemented solar supported thermal networks along with results of exemplary simulations of different system options based on real world scenarios. This document also discusses the benefits and disadvantages of large scale centralized versus decentralized solar thermal systems.