Hot water project is a process in which a group of people carry out collaborative activities in a period of time in order to achieve the purpose of individual or collective hot water demand. It is mainly used in projects such as solar hot water and heat pump hot water.
　　 With the development of human civilization, people can build larger and more complex hot water system equipment than a single hot water equipment. These devices are no longer products with a single structure or function, but have "man-made systems" that meet individual or collective demand for hot water. Thus, the concept of hot water engineering came into being, and it gradually developed into an independent subject technology.
　　In recent years, people are changing the concept of hot water engineering. It is no longer simply staying at the level of high energy-consuming "boilers". With the strengthening of people's awareness of environmental protection, new energy and green energy hot water projects that damage the environment as little as possible and do not damage the environment have gradually become the mainstream in this field. For example: solar hot water project, heat pump hot water project (air energy, ground source, water source and other technologies with certain technological content).
　　 Generally speaking, if the COP (thermal energy conversion ratio) is equal to or greater than 2, it can be defined as an "energy-saving hot water project."