Fluence SpydrX Plus LED Grow Light System vs. Fluence Under Canopy Lighting: A TCO Comparison

After six years of ordering greenhouse lighting for a commercial vegetable operation, I've made enough mistakes to keep a folder titled "Don't Do This." This article is from that folder.

Let me start with a confession: I don't care if a lighting spec sheet looks good in a spotlight font. I care about what the light map does at the third truss.

In February 2021, I approved a top-light-only layout for a 2.1-acre high-wire cucumber house. I knew I should have asked for a photon map at the lower canopy, but I thought, "what are the odds?" The odds caught up with me by March. The lower canopy looked like the area behind a bad Halloween spotlight: bright at the top, dark underneath. Not ideal. Expensive. And completely avoidable.

This is why I now compare lighting systems the same way I compare every other purchase: by total cost of ownership, not by the first line of the quote.

The comparison that would have saved me roughly $18,000 is the Fluence SpydrX Plus LED grow light system used as top lighting vs. the same system plus Fluence under canopy lighting added.

What I Compared and Why

During the 2023/2024 winter cycle, we ran two adjacent bays in the same greenhouse. Bay A used only SpydrX Plus fixtures at the truss. Bay B used the same top light layout plus Fluence under canopy light bars mounted below the crop wire. Same hybrid, same irrigation, same climate computer.

The comparison criteria were not fixture count or price per watt. They were:

• Material and installation cost
• Electricity use and photon distribution
• Crop quality and marketable yield
• Labor impact
• Maintenance risk

Dimension 1: First Cost and Installation

Adding under canopy lights is not cheap. The fixtures, cable, hangers, and labor show up immediately. In our quote, the under-canopy add-on increased the fixture and cable bill by about 40% and added roughly $0.35 per square foot in installation. If I had stopped at the purchase order, Bay A would have looked like the obvious choice.

But under-canopy bars have to be hung inside a crowded crop. You are not standing on clean concrete; you are on a work platform, trying to clip a fixture to a crop wire without snapping stems. It took two days longer than the top-light install—or rather, two and a half days, because one row had to be relocated after we realized the spray boom would catch it. That is a real cost that doesn't show up on a line item.

Dimension 2: Energy and Photon Placement

Here is the part that gets skipped in most sales conversations. A top light is great for the upper leaves. It is not great for the leaves five feet down, because the canopy itself absorbs and scatters the photons before they get there. Cranking up the top light to "push through" the canopy just overcooks the top.

Why does photon placement matter? Because a photon that hits a shaded lower leaf is doing something useful. A photon that hits an already-saturated top leaf is mostly generating heat.

In Bay B, we reduced top-light intensity by about 10-12% while keeping the lower canopy usable, because the Fluence under canopy bars were delivering photons where the crop needed them. The total electricity bill was not dramatically lower—we ran more fixtures, just at a lower output. But the cost per saleable fruit moved in the right direction.

Think of it the way off-road people set up a Can-Am Maverick X3 light bar: the high-mounted spotlight helps you see far down the road, but it leaves the ground right in front of the tires dark. You add a low-mounted bar to fill that shadow. A dense tomato canopy is the same idea, except the "ground in front of the tires" is the third and fourth truss.

Dimension 3: Crop Quality and Yield

The unexpected conclusion? The extra fixtures did not just add yield on top. They changed where the yield was.

In Bay B, the second and third tomato trusses were heavier and more uniform. We measured about 9% more marketable yield over that winter cycle—though I might be misremembering the exact number; the report is in our archive. It was one cycle, not a controlled trial, but the blocks were side by side with the same hybrid, irrigation, and climate setpoints. The biggest visual difference was not at the top. It was in the middle, where the harvest crew used to joke that the fruit "needed a flashlight."

Seeing Bay A and Bay B side by side made me realize why the details matter. Same fixture family, same climate, same crew. The only difference was where the photons were aimed.

Dimension 4: Labor: The Tradeoff Everyone Forgets

Now the honest downside. Under canopy lights are in the way. They sit in the zone where people are deleafing, lowering, and harvesting. Our crew had to learn to swing or lift the bars when they worked on the lower stems. That cost time.

It was not a net disaster, though. In Bay A, we spent more hours stripping dying lower leaves because the shaded leaves kept failing and hanging there. In Bay B, the lower leaves stayed functional longer, so we did not have to strip as high. Net labor was close to a wash—not the labor saving you see in marketing material, but also not the nightmare I worried about.

Dimension 5: Maintenance, Warranty, and Third-Party Baseline

Under canopy bars live in a harsher environment than top lights. They are close to irrigation lines, spray residue, and mechanical damage. We have not had a failure in the first 18 months, but I budget for one. I checked the DLC horticultural listing before committing, and I used the photometric files from Fluence's website instead of trusting the brochure. Reference: DLC Qualified Products List, accessed Dec. 2024; Fluence published photometric files.

The DLC listing is not a guarantee of crop results, but it gives me a third-party energy-performance baseline. That baseline makes the TCO calculation much easier.

The Mistake That Changed My Checklist

Here is the mistake I keep replaying. I assumed "same DLI at the top of the canopy" meant same crop performance. I did not verify what the light was doing at the fruit zone. It turned out the limiting factor was the middle and lower canopy all along.

If you are not measuring light where the fruit is being produced, you are not comparing lighting systems—you are comparing fixtures.

Now my checklist for every lighting quote:

• Ask for PPFD values at the top, middle, and lower crop zones, not just at the fixture height.
• Run the light plan using the crop's leaf area at month three, not the first week.
• Add the labor to install, maintain, and remove the fixtures.
• Calculate TCO: material + installation + electricity + labor + risk against saleable yield.

Which Configuration Should You Choose?

If you grow short crops or use lighting for only a short finishing period, the top-light-only configuration can still make sense. The under-canopy bars add material, labor, and crop-change time that you may never recover.

If you grow high-wire tomatoes, cucumbers, or peppers into the dark months, the comparison changes. The lower canopy is a revenue zone, and under-canopy lighting is a way to protect that revenue. In our high-wire cucumber house, the combination won on TCO. In a quick-turn leafy green greenhouse, I would still buy top light only.

Bottom Line

So which is the better Fluence lighting setup? It depends on where your crop is losing yield. If the problem is at the top, a SpydrX Plus top-light system is the right tool. If the problem is below the top layer, Fluence under canopy lighting is not an accessory; it is part of the total system.

Comparing configurations by TCO, not by price, gave us the answer. It also gave me a checklist I wish I had in 2021. That checklist is probably worth more than the $18,000 mistake, but I'd still rather have both.