The Surface Problem: It’s Not the Light, It’s the Heat (Or is it?)
When you run a commercial grow, the first thing everyone complains about when switching to LED is the heat. Or rather, the lack of it. Honestly, I get it. For the last three seasons, we were running a mixed setup of Gavita 1000 DE HPS fixtures. The heat was manageable—you just vented hard. My first big order of the Gavita Pro 1900e LED came in Q1 last year.
Basically, I thought I had the specs nailed. I’d read all the PPFD maps, calculated DLI, and matched it to our canopy. The light they were replacing was the top-end HPS, so I figured the biggest hurdle was just wiring the new controllers. I was wrong.
The real kicker wasn't the light itself. It was the assumption that LED = Less Heat = No Problem. That's the surface issue most people talk about (and the one I fell for).
The Deep Reason: We Forgot About the Environment, Not Just the Fixture
Here’s something vendors don’t tell you (note to self: remember this for next expansion): LED fixtures don’t produce less heat; they produce different heat. A Gavita 1000 DE HPS throws a lot of radiant heat. It heats the leaf surface. The Gavita 1900e LED puts the heat into the air via the driver and heatsink.
In my first year (2023), I made the classic rookie error: I swapped the fixtures, kept the same HVAC schedule, and watched my leaf temperature drop by 4 degrees. The air temp in the room was fine, but the plants were photosynthesizing slower. I was chasing a temperature setpoint that was working against new reality. What most people don't realize is that 'air temperature' and 'leaf temperature' become two completely different metrics when you switch to high-intensity LED like the Gavita 1900.
So the deep cause isn't “the light is bad” or “LEDs don’t work.” It’s that our control logic was written for a HPS era.
The Real Cost of That Mistake
This wasn't a small error. We were running a 20-light table on that zone. The mistake affected a crop cycle of roughly 4 weeks. That error cost about $3,200 in lost yield (based on our usual grams per square foot). Plus, we had a 1-week delay in the harvest schedule, which messed up our supply chain for the next batch.
I once walked into the room and saw the controller reading 82°F. Perfect, I thought. But the leaf temps were 74°F. The Vapor Pressure Deficit (VPD) was completely off. We were essentially stressing the plants into a slow growth mode without realizing it. That's the hidden tax on a poor transition.
“Missing the environmental shift when switching from Gavita HPS to Gavita LED resulted in a 3-week production delay that took us an entire quarter to recover from.”
We've caught 47 potential errors using our new pre-check list since then. The biggest check? **Don’t look at the light, look at the room.**
The (Short) Solution: A Checklist for Your Swap
So, bottom line: if you’re looking at the Gavita Pro 1900e or any high-end LED, don’t just look at the fixture specs. Look at your environment system. Here’s the checklist I wish I had in Q1 2023:
- Don’t trust your old VPD calculator. You need to measure leaf temp directly (IR gun works fine).
- Account for different heat distribution. The 1900e puts out about 1000µmol/s, but it’s not warming the canopy like the HPS did. You might need to increase room temp by 2-3°F to hit the same metabolic rate.
- Re-evaluate your humidity target. Lower leaf temps mean higher VPD at the same room temp. You might need to run higher humidity to compensate.
- Test on one table first. Don't run a full room on the new lights without a proven environmental strategy. We tested 4 vendors and found that the first week of adaptation is critical. [Source: personal testing, January 2024].
The Gavita 1900e is a seriously good light. Probably the best commercial fixture I’ve used for uniformity and spectrum. But the light is only half the system. The environment is the other half. Get that right first.
Prices for the controller and adapters are current as of mid-2024; confirm with your distributor for the latest cost.