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Support for Energy Modeling Advancements

The Statewide Codes & Standards Utility Program supports the advancement of building energy modeling simulation tools. Utility support for the advancement of energy modeling tools includes research into implementing new technologies as well as advocating for software refinements to increase usability and effectiveness. This is accomplished through activities such as laboratory testing to collect data to support robust models as well as technical analysis to inform software adjustments.

Classroom or office with a group of people working on their desktop computers.

These activities primarily support increased compliance with California’s Energy Code through suggestions to update the Alternative Calculations Methods (ACM) documentation at the close of a rulemaking, and technical memorandum submitted to the Energy Commission for consideration as optional compliance features are added to CBECC-Res and CBECC through re-releases.

The Statewide Codes & Standards Utility Program also participates in the national conversation surrounding energy modeling tools and resources. Supporting the evolution of Department of Energy supported modeling resources benefits the global energy modeling community, including California.

The program supports the Energy Commission in updating the compliance software as needs are identified by the energy modeling community that uses them, or by Energy Commission request.



Updating T24 Software Example Project: Laboratory Testing to Support Development of Simulation of Central Heat Pump Water Heaters​


Through an Executive Director Determination in December 2019, the Energy Commission determined that a HPWH system meeting defined installation criteria may be used to show compliance with Section 1501.1 (c)8C. This determination, as well as the HPWH prescriptive sizing and layout requirements for multifamily buildings can be found on the Energy Commission Docket and website

​The Statewide Codes & Standards Utility Program is conducting laboratory testing for a range of commercially available heat pump water heating (HPWH) equipment to:​

  1. Measure the performance of a range of equipment and​
  2. Develop installation criteria for multifamily HPWH systems​

The data from this testing has been used to update the Title 24, Part 6 compliance software so it accurately simulates energy performance of central HPWH systems in multifamily buildings. The testing has and will yield a performance map of input power, output capacity, and coefficient of performance for the full range of expected conditions for each HPWH that is tested.​​

Research Questions​

There are two research questions the team is looking to answer with the lab testing data:​

  1. ​How does the equipment performance, input power, output capacity, and efficiency – coefficient of performance (COP), vary over the full range of expected operating conditions? ​
  2. What is the impact of different application configurations on total system performance? ​

Test Plan​

​If you would like more information about the testing plan and the application configurations being tested, reach out to [email protected].


​The testing has followed the schedule provided below​.

Timeline showing testing of integrated HPWH and split heat pump equipment from Q1 of 2020 through Q1 of 2024

Integration with Compliance Software ​

Using performance data collected through the lab testing described above, the California Energy Commission has and will continue to update the compliance software approved for use during the 2019 and future code cycles. Data from each HPWH unit that is tested is added to the software on a rolling basis as data is available. The Energy Commission determines the schedule for publishing updated versions of the compliance software. The below tasks have been completed and added to the software:

  • Improved the domestic hot water draw schedule to provide accurate results for multifamily buildings
  • Developed sizing methodology for multifamily Standard Design heat pump water heating systems
  • Improved distribution system modeling to account for recirculation loops and other multifamily issues
  • Added several equipment options from various manufacturers and generic options.
  • Modeled the following configurations based on test data
    • Solar Thermal Preheating available for all configurations
    • Integrated, packaged system primary system with various recirculation configurations.
    • Large single pass primary systems with various recirculation and reheating options.
  • Modeled multi-pass HPWHs in central systems based on field data to be verified and improved through ongoing lab testing.

Solutions have been utilized to allow HPWH units to be used for code compliance before results of laboratory testing were available and integrated into the compliance software. As lab results become available, the data is used to improve the software. The Energy Commission has also incorporated options for HPWHs that are not well represented by the units that will be included in the laboratory testing initiative to be used for code compliance. ​

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The Statewide CASE Team periodically distributes email notifications that advertise upcoming meetings, provide materials from past meetings, and update stakeholders on the progression of the Energy Commission’s rulemaking process. You can choose to receive measure-specific and/or general updates on these topics depending on your needs.

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