Yield & Quality: HPS vs. LED - Does One Truly Outperform?

When it comes to yield and quality, the debate between HPS and LED lighting is particularly heated. Growers on both sides claim superior results, but what does the evidence actually show? This guide examines real-world experiences and scientific findings to provide a balanced perspective.

Yield Comparisons: By the Numbers

Yield is typically measured in grams per watt of electricity used, providing a standardized metric for comparison:

These figures represent typical ranges reported by growers across various forums and growing communities. Individual results can vary significantly based on growing skill, environment, genetics, and many other factors.

"I get 2gm per Watt with LED and 1.5gm per watt with the HPS."

Quality Differences: Subjective Experiences

Quality is more subjective than yield and harder to quantify. Here's what experienced growers report:

HPS Quality Characteristics

• Density: Many growers report denser, heavier buds under HPS
• Resin Production: Some claim better trichome development and stickiness
• Traditional Appearance: The "look" many growers are accustomed to
• Aroma Profile: Some report stronger terpene profiles

"I run a 1,000 W HPS light. I switched to LED but I didn't care for it. I got bigger, fuller more solid buds with the HPS."

LED Quality Characteristics

• Terpene Preservation: Lower heat may preserve volatile compounds better
• Cannabinoid Diversity: Full-spectrum LEDs may encourage broader cannabinoid development
• Coloration: Often produces more vibrant colors (purples, blues) in strains with that potential
• Consistency: More even development across the canopy with good fixtures

"My LED grows have consistently produced more flavorful product with better bag appeal, though slightly less dense than my previous HPS runs."

Scientific Perspective

Limited scientific studies comparing HPS and LED for horticultural applications have shown:

• Comparable yields are possible with both technologies when properly implemented
• Plant morphology differs somewhat between the two light sources (LED plants often more compact)
• Secondary metabolite production (terpenes, flavonoids, etc.) can be influenced by spectrum
• LED's ability to customize spectrum can potentially optimize for specific plant characteristics

Key Factors Affecting Performance

Light Intensity (PPFD)

Regardless of technology, adequate intensity is crucial. Many disappointing results with either light type can be traced to insufficient PPFD (Photosynthetic Photon Flux Density) at the canopy level.

Coverage Uniformity

Even light distribution across the growing area is critical for consistent results. Both HPS and LED can struggle with this if not properly designed or positioned.

Environmental Management

The different heat outputs of HPS and LED require different approaches to environmental control. Failure to adapt can limit the potential of either technology.

Growing Techniques

Plants grown under HPS vs. LED may require different:

• Watering frequencies (LED typically less frequent)
• Nutrient concentrations (often lower EC under LED)
• Training techniques (accounting for different stretching patterns)
• Canopy management approaches

Hybrid Approaches

Some growers are finding success with hybrid lighting strategies:

• Mixed Fixtures: Using both HPS and LED in the same grow space
• Stage-Specific Lighting: LED for vegetative growth, HPS for flowering
• Seasonal Switching: LED in summer, HPS in winter

These approaches aim to leverage the strengths of each technology while minimizing their weaknesses.

The Verdict

Based on the collective evidence:

• Both technologies can produce excellent yields and quality when properly implemented
• Modern, quality LEDs have a slight efficiency edge in terms of grams per watt
• HPS may have certain quality characteristics that some growers prefer
• The grower's skill and environmental management are typically more important than the light type
• Personal preference and growing style should guide your choice

Rather than asking which technology is "better," consider which is better suited to your specific growing environment, experience level, budget constraints, and quality preferences.