Measure Overview
This code change proposal aims to update the mandatory methodology for allocating wattage to installed lighting wattage and update the prescriptive requirements on lighting power density
(LPD) for nonresidential indoor spaces. The LPD requirements dictate the maximum lighting power allowed in each building type or space type within a building. Consideration of the following three factors is the basis for updating the LPD values:
- The increase in light source luminous efficacy due to advancements in LED technologies since the last update in the 2022 code cycle.
- Area categories where the national standards (2025 ASHRAE 90.1) and other model codes (2024 IECC) have more stringent LPD requirements than 2025 Title 24, Part 6.
- Alignment with current industry practice in the lamp lumen depreciation (LLD) assumptions used in deriving the LPD requirements.
The revised LPD requirements do not vary by climate zone and will apply to new construction, additions, and alterations. There will be no impact on residential, Group R spaces as mandated by Assembly Bill (AB) 130. No changes to the compliance process are anticipated. While no structural or formatting change to the compliance software and documents are expected, the LPD values within the software and documents would need to be updated.
This proposal also includes a new data center-related building type for the complete building method and new primary function area for the area category method, along with corresponding LPD values.
In addition, the proposal aims to simplify the indoor lighting alteration provisions by replacing the current 5,000 ft² floor-area limitation for one-to-one luminaire alterations with a cap on the total wattage of altered luminaires. Under the proposed change, the simplified alteration pathway would apply where the total wattage of altered luminaires does not exceed 3,000 watts and the alteration reduces lighting wattage by at least 40 percent. This change maintains comparable stringency while eliminating the need to determine room or tenant space floor area to demonstrate eligibility for the simplified compliance pathway.
By integrating current technologies, good design practices, and updated standards, this code change would reinforce California’s leadership in energy efficiency and ensure future building designs maximize performance, sustainability, and affordability.
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This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, email [email protected]. Please include the measure name in the subject line.
Scope of Proposed Code Change
| Building Type(s) | Construction Type(s) | Type of Change | Updates to Compliance Software | Third Party Verification |
| Nonresidential | New construction, additions, alterations | Mandatory, prescriptive, performance | Update existing feature | No changes to third party verification |
Justification for Proposed Change
Indoor LPD requirements underwent a significant update in the 2019 code cycle and were slightly updated for a limited set of area and building categories in the 2022 code cycle. The Statewide CASE Team reviewed the current LED light source efficacy and requirements in national standards and other model codes. The LPD values for certain spaces in these standards and model codes are already lower than the LPD values in the 2025 Title 24. ASHRAE 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings) has already published lower LPD values for some spaces in Addendum S to ASHRAE 90.1-2022 and the same general lighting LPD values have been proposed for the 2027 version of IECC (International Energy Conservation Code). The Statewide CASE Team also recognized that the light loss factors, specifically, the lamp lumen depreciation (LLD) values used to derive the LPD values for past code cycles, have been based on factors for traditional light sources, despite the underlying technology for the LPD values already being LED. This appears to be inconsistent with current industry practices and should be updated accordingly.
Current code requirements have not explicitly addressed LPDs for data centers and the related spaces. Given the rapid growth in data center construction to support cloud computing and artificial intelligence, it is critical to ensure illumination services are provided with high energy efficiency in data centers. Therefore, the Statewide CASE Team recommends including data centers and related spaces as part of the effort in updating the LPD requirements.
Updating the LPD requirements presents a significant opportunity for savings, highlighting that lighting remains one of the most impactful building end-uses for reducing energy demand and the carbon footprint of nonresidential buildings.
Relevant Documents
CASE Reports
Round One Utility-Sponsored Stakeholder Meeting Materials
Round One Utility-Sponsored Stakeholder Meeting Materials
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Give Us Your Feedback
The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.