Domestic water heating (DHW) accounts for a significant share of multifamily building energy use, especially in California's coastal towns. While each new construction project will have a different ratio of energy end uses, one can look at the existing building stock to get an idea of how much is attributable to DHW systems. According to the Department of Energy's Residential Energy Consumption Survey (RECS), DHW accounted for around 32% of overall energy use for existing multifamily units in the late 1990's.

DHW can be installed on a unit-by-unit level through individual water heaters or a building-wide basis using a single water heating device, such as a boiler, to provide hot water for multiple dwelling units. This second category is known as a central DHW system.

The following design guide, intended for building owners, developers, and designers, provides an overview and introduction to central DHW systems by:

1. Highlighting the basics of the regulatory context in California (Title 24)
2. Discussing the major opportunities for energy savings and improved service to tenants through improved systems, many of which have arisen from recent advances in heater and boiler technology and advanced control systems
3. Identifying common design problems and mistakes