W6. Install Summertime Water Heaters

Description

Combination heat and hot water boilers are designed to provide both heat and hot water in a single system. During the winter, the boiler provides both heat and hot water, but during the summer, the boiler provides only hot water because no heat is needed. These systems can be fairly efficient in the wintertime, when the boiler is running at full capacity. However, during the summer, they tend to be very inefficient because the boiler is running at very low capacity.

There are a few different types of combination heat/hot water boiler systems. This ECM applies to the following two types: (1) systems where there is a tank on the boiler (sometimes called a "side-arm" water heater) that has an internal coil that boiler water runs through to heat the water in the tank; (2) systems where water is heated in a coil inside the boiler. Other types of combination systems—in particular, systems where several smaller boilers provide heat, and only a few are used for hot water in the summer—are generally not inefficient enough to merit installation of a separate hot water heater for summer use.

Applicability

• Multifamily buildings with central combination boilers for heat and hot water

Types

• "Side-arm" water heater
• Heater coil inside the boiler

Considerations

• In most cases, the separate domestic water heater heater should operate only during the summer months because in the winter hot water is generally more efficiently generated by the central boiler.
• Installing a separate domestic water heater presents an opportunity to change to a less costly fuel type.

Performance/Economics

• Installing a separate water heater to provide hot water during the summer months can provide efficiency gains of 25 percent or more.
• Performing this ECM in several PHAs has shown savings results ranging from zero to more than 25 percent.

Resources/Links

Energy Conservation for Housing – A Workbook, HUD, September 1998. Page 7-161 addresses installing summertime water heaters.

Energy Performance Contracting for Public and Indian Housing: A Guide for Participants, HUD, February 1992. Pages 26 and 27 address domestic water-heating systems using performance contracting.

Improving Energy Efficiency in Apartment Buildings, American Council for an Energy-Efficient Economy, 1995. ISBN 0-918249-23-6. Pages 104 through 115 address domestic water heaters.

Consumer Guide to Home Energy Savings, American Council for an Energy Efficient Economy, 1999, ISBN 0-918249-38-4. Pages 117 and 118 address using tankless coil and indirect domestic water heaters.