7 Advantages of Under-Canopy Lighting (and When Not to Use It)

Most flower rooms are lit from one direction. The top of the canopy gets everything the fixture can give; the bottom third gets what filters through. Under-canopy lighting fixes the one problem top lights cannot fix by adding more watts: light that never reaches the lower bud sites. Here is what that buys you, where it does not help, and how it compares with simply hanging more top light.

1. Light reaches the bud sites that top light misses

Leaves absorb most of the photosynthetically active light that hits them. Once the upper canopy closes, the lower sites sit in shade no matter how strong the fixture overhead is. Raising the top-light intensity mostly pushes the upper flowers harder and adds heat at the top of the plant. Bars placed between the plants put light directly on the sites that were starving. In our customers' rooms, adding AG-140 under-canopy bars as supplemental lighting has increased yield by up to 30%. A 2025 peer-reviewed study measured up to +24.58% and +29.95% yield gains from under canopy lighting (read the study).

2. A more even canopy, top to bottom

The lower flowers are not only smaller under top-only lighting, they finish later and looser. Under-canopy light evens out intensity and, with it, leaf temperature and VPD from the top of the plant to the bottom, so the whole plant matures on a closer schedule. That shows up at trim as fewer small, airy buds in the bottom of the bin.

3. Watts go where they are needed

Compare two ways of adding roughly 1,800–1,900 µmol/s to a 4 × 8 ft bed:

Option	Fixtures	Added power	Where the light lands
Add top light	1 × 640 W full-phase fixture	640 W	Top of the canopy, already the brightest part of the plant
Add under-canopy	4 × AG-140 R80 Red bars	560 W	Lower and mid canopy, the part that was in shade

The under-canopy option uses fewer watts and puts the photons on tissue that had none. For a room that is already near its top-light intensity target, it is the only option that adds usable light instead of surplus.

4. No extra heat at the top of the plant

More top light means more infrared and more driver heat right above the flowers, which is where heat stress and bleaching start. Under-canopy bars spread 140 W each across the bed at plant level, so the added heat is small and distributed rather than concentrated above the canopy.

5. Built for the wet part of the room

Bars that sit between plants get sprayed, dripped on and washed down. The AG-140 is rated IP65, so routine IPM spraying and washdown do not require pulling the bars out first.

6. Scales from one bed to a whole facility

Each AG-140 carries power and dimming through a single connection and plugs end to end into the next bar, with no separate data cable. One power cord feeds up to 10 bars at 120 V or 24 at 277 V. A single Master Controller drives up to 100 bars directly (50 per side), and the signal booster built into every bar lets one group run up to 1,000 bars, and the bars also work with Trolmaster Hydro-X or any 0–10 V controller. That means the same part number works for a two-bar trial and a full build-out.

7. It can qualify for a utility rebate

The AG-140 is DLC listed. The R80 Red version is rated at 3.25 µmol/J, which clears the 3.24 µmol/J efficacy floor that Southern California Edison's agricultural program set for 2026 fixtures. See our rebate guide for the current SCE and PG&E per-fixture amounts and the application steps.

Where under-canopy lighting is not the answer

• Short, single-cola plants (sea of green). There is no lower canopy to light.

• Veg and mother rooms. The goal there is compact, healthy growth, not bud development; spend the money on top light with a 5K spectrum.

• Rooms that are under-lit on top. If your top-light PPFD is well below target, fix that first. Under-canopy bars supplement a well-lit canopy; they do not replace top light.

How to start

A two-bar kit under one 4 × 4 ft bed, run next to an identical bed without bars, is the cleanest test. Weigh the two harvests. The AG-140 Under Canopy LED Kit includes the bars, power cord, jumper cord and stands in one box. For bar counts by bed size, daisy-chain limits and the full cart list, read How many under-canopy light bars do you need?

Questions about your layout? Email info@growerschoice.ag with bed dimensions and supply voltage.

Browse all under canopy lights, or start with the AG-140 Under Canopy LED Kit.