Controlled Environmental Horticulture: Lighting Efficacy & Language Clean-up
Measure Overview
Currently, the Title 24 Part 6 code requires luminaires and lamps that are used for plant growth to have a minimum photosynthetic photon efficacy (PPE) of 2.3 micromoles per joule (µmol/J). The proposed code change would increase the mandatory PPE requirement for controlled environment horticulture (CEH) to a minimum threshold of 2.5 µmol/J. The proposal references the ANSI/ASABE S640 standard for measuring horticultural lighting performance within the photosynthetically active radiation (PAR) range of 400-700 nanometers and aligns with the Design Lights Consortium (DLC) Horticultural Technical Requirements V4.0.
The proposed requirement would apply to new construction, additions, and alterations in greenhouse and indoor CEH spaces with an aggregate horticultural lighting load of 40 kW or greater. The minimum PPE requirement would apply uniformly across all crop types. The proposal would revise the mandatory requirements outlined in Section 120.6 (mandatory requirements for Covered Processes). The increased efficacy requirement is intended to reflect the current lighting performance industry standard. As documented through the adoption of 2.5 µmol/J as the efficacy level in standards such as ASHRAE 90.1 and product listings in the upcoming version 4.0 of the DLC Horticultural Qualified Products List (QPL), this alignment demonstrates the availability of the products in the marketplace.
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This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, submit feedback to [email protected]. Please include the measure name in the subject line.
View the Energy Commission's proceedings and available proposed code language by visiting their CEC 2028 Proceedings Website page.
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 | No updates | No changes to third party verification |
Justification for Proposed Change
The proposal builds upon the 2025 code cycle requirement and is expected to provide incremental energy savings with minimal cost impact, as 2.5 µmol/J fixtures are now widely available throughout the market. The updated efficacy threshold will set required efficacy more than 45% above the most efficacious non-LED horticultural lighting option, the double-ended high-pressure sodium light.
This measure is expected to have a straightforward compliance pathway, as most growers who have already adopted, or will be planning to adopt, LED technology will use fixtures with an efficacy of at least 2.5 µmol/J. The incremental increase from 2.3 to 2.5 µmol/J would disqualify only about 12% of products that were previously compliant. Additionally, CEH operators seeking utility rebates for horticultural LEDs are already required to use fixtures listed on the DLC Horticulture QPL, further aligning this proposal with California utility program incentive requirements.
Relevant Documents
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.