ET25SWE0045 - HVAC Tool Validation Phase 2
The PG&E HVAC Tool, developed to estimate savings for retro-commissioning (RCx) measures in commercial buildings pursuing utility incentives in California, has faced limited adoption due to the need for additional validation and California Public Utilities Commission (CPUC) approval. To address this, the project team (Phase 1) validated the Tool using EnergyPlus (E+) models, comparing results for Air Side and Hot Water System measures. The analysis involved 132 runs across four DEER commercial prototypes (Retail, Office, Education, and Manufacturing) and three California climate zones (mild, hot, and cold). The report details the modeling procedures, savings comparisons, sensitivity analyses, and identified discrepancies between Tool and model estimates, including sources of uncertainty. Recommendations for improving the Tool’s accuracy and usability are provided to encourage adoption by IOU managers, implementers, and CalTF staff, increasing the likelihood of CPUC approval.
The proposed idea is to build on the completed CalNEXT project ET23SWE0060 - “PG&E HVAC Tool Validation” with updates, improvements, and additional HVAC equipment types and parameters.
The California Technical Forum (CalTF) and Pacific Gas & Electric Company (PG&E) requested that TRC implement recommendations from PG&E HVAC Tool Validation Study (ET23SWE0060) to comply with program requirements and strengthen tool accuracy and applicability. They also requested that temperature reset fan and pump penalties and zone level minimum VAV calculations are examined.
TRC proposes to update Airside, hot water (HW) and chilled water (CHW) system calculations. The airside updates include more recent fan curves, supply air reset calculations, and zone control. The hot water side updates include boiler sequencing and reset while the chilled water updates include the addition of air-cooled systems and reset calculation improvements.
The results of this work will maximize the effectiveness of the HVAC tool for users, developers, program administrators and evaluators, increase tool understanding, and minimize uncertainty when using the tool to forecast and verify energy savings claims and incentives.
The HVAC Tool is designed to estimate energy savings from commercial HVAC retro-commissioning (RCx) and operational measures, but the Phase 1 validation revealed calculation limitations that reduced stakeholder confidence and constrained broader program use. This project addressed the need to improve the tool’s technical defensibility, usability, and applicability for utility program implementation and evaluation.
In Phase 2, the project team enhanced the tool’s airside, hot-water, and chilled-water system calculations through a series of targeted updates. These included revised fan curves based on the Title 24 Alternative Calculation Method, improved supply air temperature reset fan penalty calculations, zonal variable air volume minimum airflow inputs, corrected boiler calculation errors, boiler sequencing, improved hot-water reset logic, support for air-cooled chillers, refined chilled-water pump penalty calculations, and updated Climate Zone 2025 weather data. The modified tool was validated against benchmark data from real projects, Title 24 compliance models, and engineering calculations.
Results indicate that the updated HVAC Tool provides improved technical consistency, reduces unrealistic fan and pump penalties, expands equipment coverage, and produces more reliable savings estimates. Stakeholder feedback also informed improvements related to transparency and usability. The project successfully met its objectives by implementing planned modifications, documenting the methodology, and validating the revised calculations.
Overall, the updated HVAC Tool strengthens the credibility of savings estimates for utility program applications and provides a practical handoff package for future use, review, and maintenance. Additional recommendations were identified to further improve usability, calculation accuracy, reporting functionality, and developer-oriented documentation, supporting broader adoption across California IOU RCx HVAC programs.