A Utility Grow-Lamp Cheat Sheet

AMPhoto_Marijuana_086I was previously an electric utility energy efficiency analyst. If you know what that means, you must be utility staff and this article is for you! I became fascinated with the enormous electric consumption of the newly-legalized cannabis industry in my home state, Washington. For the past three years, I’ve focused solely on reducing the energy impact of cannabis by leveraging utility dollars to help growers purchase efficient grow lamps. As cannabis operations open across the United States, I have interacted with many electric utilities that are uncertain about how to handle rebate requests from growers. Below is my attempt to summarize key understandings and most common methods established by utilities.

Jump In!
You are joining dozens of electric utilities around North America who have paid cash incentives to cannabis growers.  I have personally confirmed with 63 utilities that have criteria for offering rebates in 18 states and 5 providences. These utilities understand that cannabis is a new industry with a huge energy appetite. And rebates have a strong influence on equipment purchase decisions. Utilities want to avoid “Lost Opportunity” in this new market and accelerate preferred technologies. Therefore, it is responsible to offer rebates, even if offerings shift as better information emerges. Utilities with close ties to the Department of Energy (I’m looking at you, Bonneville utilities), can still fund projects with their “self-funded” budget.  Conservation is still the lowest cost resource whether the savings come from a home appliance or a cannabis farm. State regulations validate this industry – go for it!

Horticulture Lighting is not “Lights”
Grow lights are a part of an industrial process that happens to produce light. The name “grow lights” can be misleading, and tempting to run projects through established lighting programs. Lights are attached to a building for the purpose of human occupancy and are always related to human vision. The purpose of Grow Lamps is to transmit photon energy to plants through specific light spectra. Grow Lamps happen to illuminate a room (albeit in an eerie way) but their purpose is a component of industry.

Lighting for “Veg” and “Flower” is Different
Hours of operation is the biggest input for cannabis rebate projects. It is simplest if growers have designated lights (or rooms) specifically for vegetative or flowering purposes. From an energy perspective, the stages “Vegetative”, “Clone”, “Nursery”, or “Mother” are all “Vegetative” or “Veg”. During Veg, general growth of the plant is encouraged and lights are used for 18-24 hours each day to mimic long summer days. Plants are then moved to the “Flower” stage where lights are reduced to around 12 hours each day to mimic autumn. This reduction in light triggers plants to flower or “bud”.

All Jobs are Custom
Because cannabis rebates do not fit into standard lighting programs, for the time being, all jobs must be treated as custom by utility staff. Structure and methods from established lighting programs (such as “hours of operation” and “wattage”) might be helpful, but not for qualifying criteria. A specific qualifying product list such as Design Lights Consortium or Energy Star should not be used. Because Grow Lamps are a horticulture industrial process they are unrelated to building code, especially when establishing baseline.

Establish Baseline – Imperfect but Acceptable
At this time it is not sufficient to rely on existing qualified product list for lighting.  These lists do not pertain to horticultural lighting.  Utilities need a horticulture-specific baseline, or in the meantime a solid understanding of what is “industry standard practice.” The best thing we have right now is the 2011 Evan Mills Study, which surveyed growers and offered an excellent framework for studying energy usage. The Mills study asserts that a 1,000-watt single-ended fixture over 16 square feet of canopy is a typical flower baseline, and a 600-1,000 watt single-ended fixture over 16 square feet is a good vegetative baseline.  I believe this is a good baseline for now – until further research arrives. Because so much has changed since 2011, I hope Evan Mills has an updated study on the way.

Learn, Don’t Tell
Because cannabis rebate jobs are custom, it is important for the utility to document how each business operates,  without telling growers how to grow. For example, during the vegetative stage some growers prefer to keep lights on 24 hours/day, others 18. Some turn lights off each week for routine maintenance, others do not. Although most growers I know use 12 hours/day for flower, I’m sure someone out there uses 13 or 11.  It is also good to establish the expectation that incentives are based on actual energy (and power) use, and that deviations from what they reported in the rebate application may result in a partial refund of incentives paid.

Equipment Basics
So what are the equipment choices growers are making? The specifics vary greatly, but here is a general overview:


Also called

Cost / Fixture





T5, T8
Baseline. Legacy technology, serviced by mass market (such as Philips)
Metal Halide – Single Ended*
Baseline. Technology designed for parking lots, warehouses, high bay lighting, not designed for cannabis
High Pressure Sodium – Single Ended*
Veg + Flower
Baseline. Technology designed for parking lots, warehouses, high bay lighting, not designed for cannabis
Double Ended High Pressure Sodium*
DEHPS “Double Enders”
Veg + Flower
Medium – high efficiency.
Ceramic Metal Halide*
315 or 630
Veg + Flower
Medium – high efficiency. Not new technology but relatively new for cannabis
Light Emitting Diode
Veg + Flower
High efficiency. Highly customizable form factor spectrum
Medium – high efficiency. Replaceable bulbs available.
Medium efficiency. Similar to fluorescent.

*Considered High Intensity Discharge Fixtures (HID).

HVAC Savings
All indoor cannabis operations use air conditioning to reduce the temperature of their rooms, 365 days of the year, 24 hours of the day …. even in Alaska! The heat emitted by grow lights is so high, the room must be cooled to please the cannabis plant. Efficient grow lamps emit significantly less heat, which means less air conditioning. An additional 25-40% of lighting wattage will be used through HVAC to cool rooms and manage humidity. These are real savings – do no omit them from your calculations and please offer incentives for these positive energy impacts.

Understanding Greenhouses vs. Indoor
Greenhouse operations generally differ in two ways from an energy perspective: the plants stay relatively still, and they rely to some degree on energy from the sun. Therefore, instead of moving plants from a “veg” to a “flower” room , the lights’ hours of operation be a weighted average of days in veg versus days in flower. Additionally, natural sunlight will affect the actual hours that the lights will be in use. You might assume lights will operate 50-80% of the normal plant photoperiod, depending on climate and growing style.

Pay Quickly
Because cannabis growers are cut off from traditional lines of credit, they are even more cash-strapped than other start-ups. Utility incentive dollars have a real, positive influence on equipment purchase decisions. However, the wait time between a grower purchasing lights, and receiving utility dollars can be months. Please, respect these growers’ desire to do the right thing – pay them quickly so their decision to invest in efficient equipment does not affect their ability to run operations in the meantime.

I hope this helps encourage you to say “yes” to offering cannabis rebates. Please let me know if there are additional topics you would like covered or questions answered.