California’s energy code, Title 24 2022, became effective January 1^st, 2023. In it were new code requirements for indoor horticulture spaces, including grow light requirements. This was in part motivated by a large surge in energy use after the 2018 legalization of recreational cannabis in the State. Urban indoor grow facilities took off and energy use increased 162% in 2022 over 2017.

The regulations define Controlled Environment Horticulture (CEH) and set requirements for lighting, HVAC, dehumidification, and greenhouse envelope. There are two primary approaches to Title 24 requirements on grow lights:

1. Minimum efficacy requirements, and
2. A time-switch and multi-level lighting control requirement.

These requirements apply to new construction, additions to existing CEH facilities, conversion of a warehouse to a CEH, and replacing 10% or more of current grow lights in an enclosed space.

Minimum Photosynthetic Photon Efficacy (PPE):

These requirements apply to facilities with more than 40kW of total connected horticultural lighting load, INCLUDING general lighting.

• For defined indoor growing facilities, all grow lights, including those with removable lamps, should have a PPE rating of at least 1.9 micromoles per joule (µmole/J).
• For Conditioned Greenhouses, all grow lights should have a PPE rating of at least 1.7 micromoles per joule (µmole/J).

Time-switch and Multilevel Lighting Controls:

Time-switches and multilevel lighting controls are required for both indoor growing facilities and greenhouses. The energy code also requires designing electrical power distribution systems serving CEH spaces in a way that allows monitoring the energy use of the aggregate horticultural lighting load.

California Title 24 standards are enforced by local and county building inspectors. Anyone involved in designing new indoor horticulture facilities or creating additions or conversions should be knowledgable of new Title 24 CEH requirements.

The CEH regulatory language begins on page 192 of this document.

Image: Thrive Agritech

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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