Measure Overview
Daylight Responsive Controls for Greenhouses
The proposed code change would introduce a new mandatory control requirement for greenhouses with supplemental electric lighting. The requirement would apply to greenhouse facilities with more than 40 kW of connected horticultural lighting load and would provide two compliance options:
- Option 1: Timeclock + PAR Sensor-Based Control
Combines a scheduling device with on/off or dimming control in response to real-time Photosynthetically Active Radiation (PAR) levels. - Option 2: Daily Light Integral (DLI) Control
Automatically adjusts supplemental lighting based on cumulative Photosynthetic Photon Flux Density (PPFD) measured over the daily photoperiod to meet—but not exceed—a user-defined DLI target.
The proposed code change would apply to both new construction and alterations of greenhouse facilities. It is not climate-zone dependent, and no compliance software updates are anticipated. However, to ensure the proper functionality of the required controls, an acceptance test protocol for use by field technicians at the time of installation may be considered.
Language Clean Up
The proposed code change would also clarify requirements for indoor grow facility lighting controls. The current code requirements for control strategies can be interpreted to imply that a simple time switch is sufficient and that astronomical time switches are appropriate for indoor growing. This code language clean-up would specify that automatic scheduling devices capable of dimming the horticulture lighting and turning it on/off are required for indoor grow facilities.
In addition, the proposed code change would move the indoor grow facility electrical power distribution systems requirement – currently in the broader Controlled Environment Horticulture (CEH) section – into the CEH Lighting Controls section and explicitly include greenhouse lighting under the same 40 kW threshold.
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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 | Add new verification requirements |
Justification for Proposed Change
Daylight Responsive Controls for Greenhouses
CEH is one of the fastest-growing energy end-uses in California. Greenhouse facilities with supplemental lighting are expanding rapidly to support cannabis, leafy greens, and vine crops, and these systems are highly energy intensive. Without stronger controls, this sector risks locking in years of unnecessary energy use, higher operating costs for growers, and additional strain on California’s electrical grid.
The proposed daylight responsive controls would deliver measurable and persistent energy savings ranging from an estimated 9%1 to 26%2 while improving crop consistency and grower control. By automatically adjusting lighting in response to daylight availability, the measure ensures that plants receive the optimal amount of light each day, avoiding the waste and inefficiency of over-lighting. This reduces electricity use and lowers cooling loads, reducing grid demand during critical hours.
The proposal provides growers with flexibility and choice. They may select between a timeclock + PAR sensor pathway or a more advanced Daily Light Integral (DLI) pathway. Both reduce wasted energy, and the DLI option enables even greater savings and performance improvements. Importantly, the measure is designed to be practical: it does not impose additional software burdens, and compliance verification would remain straightforward, with possible enhancements through an acceptance test protocol.
From a policy perspective, this proposal builds directly upon the 2022 and 2025 Title 24 CEH measures, which first set minimum PPE requirements for horticultural lighting. By layering in controls, Title 24 can create a natural next step in California’s multi-cycle strategy for CEH efficiency and decarbonization.
Language Clean Up
Under the current language, some stakeholders may interpret a simple time-switch—or even astronomical time-switch controls—as sufficient for indoor growing facilities. However, these approaches do not always adequately address the dimming requirements in the current code language, which ensures the controls can respond to the lighting needs of crops in indoor grow environments. The proposal would close an existing compliance gap by explicitly stating that automatic scheduling devices capable of dimming the horticulture lighting and turning it off are required, preventing misapplication of lower-performing strategies in energy-intensive facilities.
The language clean-up proposal would also simplify compliance verification for building officials by consolidating the electrical power distribution monitoring requirements into the CEH Lighting Controls section and extending them to greenhouse facilities under the same 40 kW threshold. This ensures consistent treatment of CEH lighting systems, reduces ambiguity for enforcement staff, and streamlines compliance forms for project teams. By clarifying compliance pathways, the proposal minimizes confusion in plan review and field inspection, addressing one of the most cited barriers to effectively enforcing CEH measures.
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.