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NSHP Program

Solar Water-Heating Systems for New Homes

Solar Water Heating Systems Can Contribute to Efficiency Standards Compliance and New Solar Homes Partnership Energy Efficiency Requirements

Energy Impact of Water Heating

Water heating energy use makes up a significant portion of total energy use for residential buildings. In California's mildest climates water heating energy use may equal the combined energy needed for space heating and space cooling. A solar water heating system can contribute thirty to 80 percent of the energy needed for residential water heating (depending on the design of the solar water heating system). The contribution of a solar water heating system can be claimed as credit toward compliance with the Title 24 Building Energy Efficiency Standards and also for qualification for the New Solar Homes Partnership or other incentives programs that require specified savings beyond the standards.

Calculating the "Solar Fraction"

A solar fraction (SF) must be calculated to determine the energy credit for a solar water heating system. The SF is the percentage of energy that the solar system contributes to the building's total water heating energy requirement. Solar equipment must be listed in a Solar Rating and Certification Corporation (SRCC) directory. The Commission uses two SRCC rating methods. The Certified Solar Collector Testing and Rating Program (OG100) rates collectors that are used as components of a "built-up" system. The Certified Solar Water Heating System Rating Program (OG300) rates complete solar water heating systems. The rating from either test method can be used to determine an SF by using one of the Commission's approved solar water heating calculation tools (see Links below).

Use of the Solar Fraction to Determine Overall Building Energy Use

The impact of the SF on the overall energy use of the building must be determined with an Energy Commission-approved building energy compliance software program. A link to the list of the software applications approved for use with the California Building Standards is provided below. The SF should be entered into the building energy compliance software program as part of the water heating systems input data. Refer to your program's user's manual for detailed directions on how to enter the SF value.


The following forms are required:

Solar Water Heating Calculations
Click on the test method you intend to use:

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