Fluence Under Canopy Lighting: A Quality Manager's Head-to-Head vs. Traditional Top Lighting

Why We Decided to Compare Under Canopy vs. Top Lighting

If you've ever walked through a dense tomato or cannabis canopy, you know the problem: the lower leaves get maybe 10–20% of the light the top receives. Five years ago, everyone just accepted that. But the industry has shifted—seriously. What was best practice in 2020 (just blast more light from above) is now being replaced by inter-lighting and under canopy solutions.

In our Q1 2024 quality audit, we reviewed five different under canopy systems. One of them was Fluence's SPOTLIGHT NETWORK with their Discovery SPOTLIGHT fixtures. I'm not here to tell you it's the absolute best—no single product fits every grow. But I can show you how it stacks up against the traditional top‑lighting approach we've used for years. I'll focus on three dimensions that matter most to a quality inspector: light distribution uniformity, installation & flexibility, and long‑term reliability.

Quick note before we dive in: this comparison is based on our specific setup—a 50,000‑sq‑ft multi‑tier greenhouse with mixed crops. Your mileage may vary if you're dealing with single‑layer benches or tall vine crops.

Dimension 1: Light Distribution Uniformity

Traditional top lighting (we used 1000W HPS fixtures on 8‑ft centers):

• PPFD at canopy top: ~800 µmol/m²/s
• PPFD at lower canopy (30 cm down): ~150–200 µmol/m²/s
• Variation across rows: ±15% on top, ±40% in the middle

Fluence Discovery SPOTLIGHT with under canopy bars (we installed one bar per row, 4‑ft length, 0.5 m above the lower canopy):

• PPFD at lower canopy: 350–400 µmol/m²/s
• Variation across the row: ±5% (measured in 6 zones)
• Top canopy PPFD remained unchanged (no shadow projection issues)

The difference was way bigger than I expected. With the Fluence bars, the lower leaves suddenly went from survival mode to active photosynthesis. I ran a blind test with our head grower: same row, one side with Fluence under canopy, one side with only top light. He picked the Fluence side as 'way denser lower nodes' without knowing which was which.

But here's the nuance—the uniformity advantage only matters if your crop actually has a tall canopy. For short crops like lettuce or microgreens, top lighting is still perfectly fine. From the outside, people assume under canopy lights always help. The reality is they only pay off when you have at least 1.5 m of vertical leaf mass.

Dimension 2: Installation & Flexibility

This is where I had a serious love‑hate moment. Traditional top lights are dead simple: hang them, wire them, done. But they also require a superstructure, cable trays, and you're stuck with the grid once it's up.

Fluence SPOTLIGHT NETWORK uses a daisy‑chain system with quick‑connects. Each 4‑ft bar weighs maybe 8 lbs. The installation kit includes mounting brackets that clamp onto standard trellis poles. Sounds great, right?

Our install team did the first 5 rows in about 45 minutes. Then we ran into a problem: the cable lengths between bars were just a bit short for our row spacing (6 ft centers). We had to order extension cables—that added a week to the timeline. In hindsight, I should have measured the exact distance and ordered the right kit upfront. But with the CEO pushing for a mid‑cycle retrofit, I made the call with incomplete specs. That mistake cost us about $2,200 in extra shipping and labor.

On the flip side, once it's installed, the flexibility is unmatched. Want to move a bar to a different row? Unclip, slide, reclip—took 10 minutes. Try that with a top‑mounted fixture. Most buyers focus on per‑fixture pricing and completely miss the cost of reconfiguring a traditional grid later. The question everyone asks is 'how much per light?' The better question is 'how much will it cost when I change my layout next season?'

Also, someone asked me recently: "Can you cut an LED light strip?" Short answer: you should not cut Fluence's under canopy bars. They are sealed units with specific lengths (2 ft, 4 ft, 6 ft). You can order custom lengths through their SPOTLIGHT NETWORK—they'll pre‑cut and terminate for you. Cutting yourself will void the warranty and risk water ingress. That's a common misconception from people used to hobby‑grade strip lights.

Dimension 3: Long‑Term Reliability & Warranty

In our facility, lights run 18 hours a day, 365 days a year. We've had top HPS fixtures that required bulb changes every 10,000 hours and ballast failures every 18 months. That's a ton of maintenance downtime.

We've been running the Fluence under canopy bars for 9 months now. So far: zero failures. The IP65 rating means dust and humidity haven't been an issue (we have high humidity in summer). The aluminum heatsink stays warm but not hot—I measured 48°C at full power.

But I want to give you a real number: we're tracking a batch of 200 units. As of today, failure rate is 0.5%. That's one unit out of 200—a driver issue, not the LED board. Fluence replaced it under warranty within 3 days. Compare that to our HPS ballast failure rate of 3–5% per year. If I remember correctly, we spent around $8,000 last year just on HPS replacement parts and labor. The Fluence system has cost zero in repairs so far.

One thing I do caution: the warranty is 5 years, but it's conditional on proper installation (correct voltage, no daisy‑chain overload, etc.). We had one grower friend who wired 12 bars on one driver—the driver overheated. That's user error, not a product flaw. Make sure you follow the SPOTLIGHT NETWORK's max load spec.

So, Which One Should You Choose?

Choose Fluence under canopy lighting if:

• You grow tall crops (tomatoes, cannabis, cucumbers, peppers) with at least 1.5 m of vertical canopy.
• You value even light distribution in the middle/lower zones and are willing to pay a bit more upfront ($1.50–$2.50 per watt installed vs. top LED at ~$1.00 per watt).
• You expect to reconfigure your layout seasonally—the flexibility pays for itself.

Stick with traditional top lighting if:

• You grow short crops (lettuce, herbs, microgreens).
• You have a fixed, long‑term layout and don't need under‑canopy supplementation.
• Your budget is extremely tight and you can't justify the additional capital cost (though total cost of ownership over 5 years may actually favor under canopy when yield gains are factored in).

Bottom line: The industry is moving toward layered lighting. What worked for your grandfather's greenhouse isn't necessarily wrong—but the execution has transformed. Fluence's SPOTLIGHT NETWORK, especially the Discovery SPOTLIGHT bars, is a solid choice if you're ready to make that shift. Just measure twice, order extension cables, and don't cut the damn strips.