Controlled Environmental Horticulture: Horticultural Lighting Efficacy
Measure Overview
The proposed code change would increase the mandatory photosynthetic photon efficacy (PPE) requirement for luminaires and lamps used for controlled environment horticulture (CEH) from 2.3 micromoles per joule (µmol/J) to a luminaire photosynthetic photon efficacy (PPE) requirement of 2.5 µmol/J. The updated requirement would align with the DesignLights Consortium (DLC) Horticultural Technical Requirements V4.0 for consistency with current industry performance criteria.
This proposal updates the definition of photosynthetic photon efficacy (PPE) to luminaire photosynthetic photon efficacy (PPE), so there is an even playing field for all products. The rating of all products will account for the optical efficiency of the luminaire and the thermal impacts of luminaire design. Otherwise, the remainder of the definition is aligned with the metric developed by the American Society of Agricultural and Biological Engineers (ASABE) for the ANSI/ASABE S640 standard. This definition will be inclusive of luminaires with replaceable, serviceable lamps.
The updated horticultural lighting efficacy requirement would apply to new construction, additions, and alterations of greenhouse and indoor CEH facilities with an aggregate horticultural lighting load of 40 kilowatts (kW) or greater. The minimum PPE threshold would apply to all crop types and system configurations meeting this load threshold. The proposal would revise the mandatory requirements in Section 120.6 (Covered Processes) of Title 24, Part 6. Since the lighting efficacy requirements are mandatory, if the California Energy Commission adopts a performance approach for space conditioning systems, the Standard Design horticultural lighting efficacy would be equal to the proposed horticultural lighting efficacy.
In addition, this measure clarifies and carries forward existing requirements already established in the 2025 Energy Code for the dimmability of horticultural lighting. Specifically, the proposed dimming functionality language is derived from the language previously contained in Section 120.6(h)5C, which requires luminaires to adhere to the multilevel lighting controls requirements in 130.1(b). The proposed language is intended to improve clarity and consistency in the interpretation and application of this existing requirement, ensuring that stakeholders clearly understand the expectations for compliant systems. This clarification does not expand the scope of regulated products or introduce new performance obligations beyond those already adopted in the 2025 Energy Code.
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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 | No updates | No changes to third party verification |
Justification for Proposed Change
California’s CEH sector is rapidly expanding to meet demand for locally grown, high-value crops produced all year. As these facilities rely heavily on electric lighting, improving fixture efficacy is one of the most effective strategies to reduce energy use. The proposed increase in the minimum PPE requirement from 2.3 µmol/J to 2.5 µmol/J ensures that new and retrofitted CEH lighting systems meet the current performance standard already commercially common.
By setting a higher efficacy threshold, the measure will deliver incremental, yet meaningful, energy savings with minimal cost impact because high-performance fixtures at or above 2.5 µmol/J are already widely available. The new threshold represents an efficacy level approximately eight percent higher than the current standard, which equates to an anticipated annual statewide energy savings of 8.1 GWh for new constructions, additions and alterations.
The proposal also enhances alignment with the DLC Horticultural Technical Requirements V4.0, ensuring that Title 24 continues to reflect the leading edge of horticultural lighting practice (DesignLights Consortium, 2025). This step builds on the 2025 iteration of the Energy Code, advancing a multi-cycle strategy to improve CEH efficiency, reduce emissions, and maintain California’s leadership in sustainable agriculture technology.
Relevant Documents
Round One Utility-Sponsored Stakeholder Meeting Materials
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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.