10 Years of LED & HPS in Horticulture: Lessons, Realities & the Road Ahead

A Decade in the Lighting Industry

Over the last ten years, I’ve seen LED horticultural lighting go from a promising technology to an industry standard. I’ve worked in optical, thermal, and lighting system design. In that time, I’ve learned that nothing is ever as simple as it seems—especially when it comes to lighting in controlled environment agriculture (CEA).

 What follows is a big-picture reflection on where we started, where we are now, and why we still haven’t completely solved for high-pressure sodium’s (HPS) role in horticulture.

From Algae to Cannabis: The Pursuit of Oil 

My journey into lighting started in 2008 at the University of Georgia, where I worked with algae grown in bioreactors to clean industrial wastewater from the North Georgia carpet industry. We tested combinations of different light wavelengths —red, blue, and green—on algae strains to maximize oil production for biofuels.

 At the time, I had no idea this experience would translate to horticultural LEDs. Fast-forward to 2014, and I found myself designing LED spectrums for cannabis cultivation in Boulder, Colorado. Back then, we were just beginning to explore how LEDs could compete with double-ended high-pressure sodium lamps (DE HPS), which had just hit the market.

The High-Pressure Sodium Reality Check

I rode the LED evangelism train for years, touting its energy savings and efficiency gains. The logic was simple: 

Replace 1,000W HPS with a 600W LED

Use less power for the same or better yield

Save tons of money on electricity

Reduce HVAC loads

It sounded great. The problem? It wasn’t always true.

Heat management was one of the biggest challenges with LEDs—one we didn’t fully appreciate at the time. HPS doesn’t just provide light; it gives evenly distributed infrared heat, which drives plant metabolism in a way that’s hard to replicate with LED alone. 

For northern growers, especially those above 35° latitude, HPS heat is a net benefit, especially in greenhouses and winter cycles. Replacing HPS with LED often requires costly HVAC and dehumidification upgrades, which many cultivators weren’t prepared for.

The Sustainability Equation: LED vs. HPS

Sustainability in horticultural lighting isn’t just about watts at the wall. It’s about total lifecycle impact—the energy, materials, and logistics that go into manufacturing, transporting, and recycling lighting systems.

HPS Lamps: Lightweight but contain Mercury, a Persistent Neurotoxin

⅓ pound per bulb (glass, aluminum, steel and ceramic arc-tube)

Minimal raw material use

Contain mercury, which requires special handling & recycling

Roughly 20,000-40,000 bulbs per shipping container

LED Fixtures: Durable but Resource-Intensive

10-20 pounds of aluminum per fixture

Heavy use of mined & processed materials

Requires heat sinks, power supplies, tooling for extrusions

No mercury, but challenging to recycle due to mixed materials i.e. potting used in drivers

Approximately 1-3000 fixtures per shipping container

The reality? HPS is infinitely recyclable—if handled correctly. Meanwhile, LED fixtures contain so much extruded aluminum and freight, by quantity and weight, that their upfront carbon footprint is substantially higher than most people realize.

LED Technology Has Limits (and We’re Hitting Them)

Most LED advancements have been driven by Haitz’s Law, which (like Moore’s Law for computing) states that efficiency gains slow as we approach theoretical maximums.

We’re already seeing diminishing returns in chip efficiency. The red and blue LEDs used in horticulture are near their physical limits, meaning breakthroughs will likely come from spectrum tuning and form factors rather than raw efficiency.

Hybrid Lighting: The Best of Both Worlds

For facilities looking to transition away from HPS, a hybrid approach is often the best move:

 50/50 or 70/30 LED to HPS allows growers to keep the infrared heat they need while gaining LED efficiency and spectral quality (most importantly, stable blue peaks).

Hybrid systems let HPS bulbs run longer (3-4 years instead of 2), extending their lifespan and cost efficiency.

This approach minimizes HVAC modifications, reducing capital expenses for retrofits.

I’ve spent years consulting with cultivators who rushed into full LED conversions only to struggle with microclimates, unpredictable drying times, and inconsistent yields. The facilities that transitioned gradually—using hybrid strategies—often performed much better.

The Financial Side of Sustainability

Every conversation about sustainability must include financial sustainability.

LED Fixtures Cost More Upfront: A quality LED fixture costs $1,000+, while an HPS system (ballast + bulb) is under $200.

Lifespan Trade-offs: Many LEDs are marketed as lasting 50,000+ hours, but in real-world conditions, some drop below 70% output within 3 years—far sooner than expected.

Warranty Realities: Warranties only work if the manufacturer is still in business. Plenty of cultivators have been left holding the bag when budget LED brands disappeared before their warranties were honored.

HPS Fixtures Are Simple: They work, or they don’t. A failed HPS ballast costs $100 to replace, while a failed LED fixture often requires replacing the entire unit.

This capex vs. opex conversation is one that most LED sales reps ignore. 

The Industry Needs a More Honest Conversation

I’ve spent a decade in the horticultural lighting industry, and if there’s one thing I’ve learned, there’s no one-size-fits-all solution. 

LED is the future, but it’s not a magic bullet.

HPS still has a place, mainly when used strategically.

Transitioning from older to newer technology always takes time.

Sustainability is more than wattage savings—it’s about full lifecycle impact.

Closing the loop on HPS recycling is crucial to keeping mercury out of the environment.

Final Thought: Let’s Make Smarter Decisions

The industry is still learning. Crop science, vertical farming, and traditional horticulture have unique needs, and lighting solutions should be tailored—not forced.

If you’re running HPS, consider a hybrid strategy. If you’re transitioning to LED, consider the long-term financials before choosing a manufacturer. Above all, if you’re retiring old HPS lamps, please recycle them.

Grow smarter and never trust a lighting salesperson.