LED vs HPS Grow Lights: The Complete 2025 Comparison Guide

Choosing between LED and HPS grow lights is one of the most important decisions for indoor growers. This comprehensive guide compares both technologies across every factor that matters: efficiency, heat, spectrum, cost, and yield performance.

LED vs HPS: Quick Comparison

Energy Efficiency: LED Dominates

Energy efficiency is measured in micromoles per joule (umol/J) - how much usable light a fixture produces per watt of electricity consumed. This is where LED technology has made the biggest gains.

In practical terms: a 400W LED can produce the same light output as a 600W HPS. Over a year of growing (12 hours/day), that's a savings of approximately $175 in electricity costs at the US average rate.

Heat Output: Managing Your Grow Room

Heat management is critical in indoor growing. Excessive heat stresses plants, increases water consumption, and requires additional cooling equipment.

How Heat Compares

Both LEDs and HPS convert electricity to heat - the difference is how much and where. HPS bulbs convert about 60-65% of electricity to heat, with most of it radiating downward toward plants. LEDs convert about 40-50% to heat, with most dissipating upward through heatsinks.

Cold climate exception: If you're growing in a cold basement or garage, HPS heat can actually be beneficial - it reduces heating costs. Some growers in northern climates prefer HPS for winter growing specifically for the extra warmth.

Light Spectrum: Full Spectrum vs. Fixed

Plants use different wavelengths of light for different purposes. Blue light (400-500nm) promotes vegetative growth and compact structure. Red light (620-700nm) drives flowering and fruiting. Far-red (700-750nm) influences plant morphology.

HPS Spectrum Limitations

HPS bulbs produce a fixed spectrum heavily weighted toward yellow-orange-red wavelengths. They're excellent for flowering but lack blue light, which can cause stretchy growth during veg. This is why many HPS growers use Metal Halide (MH) bulbs for vegetative growth and switch to HPS for flowering.

LED Spectrum Flexibility

Modern full-spectrum LEDs provide light across the entire PAR range (400-700nm), plus UV and far-red in some models. Many LED fixtures offer dimming and spectrum control, allowing growers to:

• Run higher blue percentages during veg for compact growth
• Shift to red-heavy spectrum during flowering
• Add far-red for end-of-day signals (Emerson effect)
• Include UV for enhanced terpene/flavonoid production

Cost Analysis: Upfront vs. Long-Term

The cost comparison between LED and HPS involves initial purchase price, electricity costs, replacement bulbs/fixtures, and HVAC requirements.

Yield Comparison: The Real Test

The ultimate question: which technology produces more harvest? For decades, HPS was the gold standard. Modern LEDs have changed that equation.

What the Research Shows

Studies comparing LED vs HPS yields show:

• Equal wattage: LED produces 10-20% more yield due to better spectrum efficiency
• Equal light output (PPFD): Results are nearly identical
• Cannabis specifically: LEDs can enhance terpene and cannabinoid profiles due to UV inclusion
• Vegetables: LEDs produce more compact, flavorful plants with less stretching

The key metric is grams per watt - how much you harvest per watt of electricity used. Top LED growers regularly achieve 1.5-2.0 g/W, while HPS typically maxes out at 1.0-1.2 g/W.

When to Choose HPS

Despite LED's advantages, HPS still makes sense in certain situations:

• Large commercial operations with existing HPS infrastructure and high ceilings
• Cold climates where heat is beneficial
• Very tight budgets where upfront cost is the primary concern
• Backup lighting - HPS bulbs are cheap to replace and widely available

When to Choose LED

LED is the better choice for:

• Home growers prioritizing efficiency and ease of use
• Warm climates where heat is a problem
• Limited vertical space (grow tents, closets)
• Long-term operations focused on total cost of ownership
• Quality-focused grows wanting spectrum control

Best LED Grow Lights for Different Spaces

The Bottom Line

For most indoor growers in 2025, LED is the clear winner. The technology has matured to the point where LEDs match HPS yields while offering:

• 40% lower electricity costs
• 5-10x longer lifespan
• Lower heat and simpler climate control
• Better spectrum for plant health
• Lower total cost of ownership over 3+ years

The only scenarios where HPS still makes sense are large commercial facilities with existing infrastructure, extremely tight budgets, or cold-climate grows where the heat is useful.