🔆 Why Growing Under LED is Different to HPS
Lighting technology has evolved — and so have growing methods.
While HPS and LED systems may appear similar in wattage, they deliver light in very different ways, and plant response under each system is not the same. Understanding those differences is key to unlocking full performance from modern LED grow lights.
Here’s what growers need to know.
HPS vs LED – Similar Wattage, Different Results
Although both lighting systems are designed to drive photosynthesis, the way they deliver energy to the canopy differs significantly.
HPS Lighting
- High radiant heat
- Centralised hotspots
- Narrower spectrum output
LED Lighting
- Cooler leaf surface
- Even PPFD spread
- Full spectrum output
Key takeaway: Growing methods must adapt when switching to LED in order to unlock full performance.
LED light is more efficient and more direct — which means environmental management becomes more precise and more important.
🌡️ Temperature – LED Rooms Need More Warmth
One of the biggest adjustments growers must make when moving from HPS to LED is temperature management.
The Change
LEDs do not produce the same radiant heat as HPS. That means they don’t heat the leaf surface in the same way.
What Happens If Nothing Changes?
- Slower metabolism
- Reduced transpiration
- Flat growth
Best Practice Under LED
- Increase air temperature slightly
- Target 26–28°C at canopy level
- Reduce night-time temperature drop
Key takeaway: Measure leaf temperature, not just room temperature.
Because LED fixtures run cooler at the leaf surface, environmental targets must shift to maintain optimal plant activity.
💧 Humidity & VPD – Transpiration Behaves Differently
Lower radiant heat means lower natural water movement within the plant.
Under LED, growers may notice:
- Plants drinking less
- Nutrients moving slower
- Calcium & magnesium deficiencies appearing sooner
Dial-In Strategy
- Run slightly lower RH vs HPS
- Focus on maintaining correct VPD
- Increase gentle canopy airflow
Visual cue: Thick, leathery leaves can indicate transpiration is too low.
What is VPD?
VPD stands for Vapour Pressure Deficit.
In simple terms, it’s the difference between how much moisture is in the air and how much moisture the air can hold at a given temperature. That difference drives transpiration — how plants “breathe” and move water and nutrients.
Under LED, managing VPD becomes even more important.
💡 Light Intensity & Hanging Height
LEDs deliver higher usable light.
Because the output is more efficient and directional, growers need to approach intensity differently.
Best Practice
- Start lights higher and dimmed
- Increase intensity gradually
- Maintain an even canopy
- Avoid central hotspots
Stress Indicators
- Leaf tacoing
- Hard praying
- Growth stalling
If plants show stress, raise the fixture or dim output accordingly.
🌬️ Airflow & CO₂ – Stability Matters
LED rooms thrive in stable environments.
LED Room Advantages
- Cooler
- More controllable
- Highly efficient
Performance Boosters
- Strong canopy-level airflow
- CO₂ supplementation (in sealed rooms)
With CO₂
- Higher temperatures can be tolerated
- Feeding limits can scale with metabolism
LED technology rewards precision — airflow and environmental control should scale with light intensity.
🌱 Feeding & Nutrition – More Light ≠ More Feed
A common mistake when switching from HPS to LED is feeding the same EC.
Under LED:
- Slightly reduce EC
- Prioritise nutrient uptake, not strength
- Ensure calcium & magnesium availability
- Monitor new growth closely
Important: Overfeeding causes lockout faster under LED conditions.
Plants may drink less under LED due to lower leaf surface heat, meaning salts can accumulate more quickly if feeding is not adjusted.
In Summary – What to Change When Switching to LED
Add:
- Leaf temperature monitoring (IR gun or sensor)
- Calcium & magnesium support
- Dimmable lighting control
- Even canopy airflow
Reduce:
- High EC feeding
- Overwatering habits
- HPS-style light distances
- Reliance on air temperature alone
Switching to LED isn’t just a fixture upgrade — it’s a method adjustment.
🔦 Featured LED Solutions
Explore our high-performance LEDs designed to support modern growing environments:
Omega 720W Range
The Omega Black delivers powerful 720W output, providing strong light intensity for optimal growth. Supplied with a 600W Black ballast, it balances performance and energy efficiency while keeping operational costs controlled.
The Omega 720W Plus delivers intense, uniform light coverage with high Photosynthetic Photon Flux (PPF), saturating grow spaces for vigorous plant development. Its integrated driver design keeps installations sleek and compact.
Photon 720W LED
The Photon 720W is built for simplicity and performance, featuring:
- Plug & Play technology
- Built-in driver
- Superior full-spectrum LED output
- 0–100% dimming control
- Built-in daisy chain connectivity
A reliable solution for growers who want efficiency without complication.
Omega Infinity LED Range
Engineered for growers who demand control and scalability, the Infinity range is available in:
Each model delivers uniform light distribution, high efficacy, full dimming control, and efficient thermal management — making it a professional alternative to traditional lighting systems across both compact and commercial environments.
The Bottom Line
LED technology doesn’t replace HPS — it changes how growers manage:
- Temperature
- Humidity
- Transpiration
- Feeding
- Airflow
- Light intensity
When dialled in correctly, LED systems deliver efficient, controllable, and highly productive grow environments.
If you’re supporting customers transitioning from HPS to LED, understanding these differences ensures smoother installs, better advice, and stronger long-term results.
Thanks for growing with Eden 🌱
Our team is always here to help.
📞 01952 455725
🌐 www.edenhorticulture.co.uk
📱 WhatsApp: 07307 336 739
