LED vs. HPS: Which lighting is the best choice for indoor cultivation?

Introduction

LED vs. HPS: Lighting is a crucial factor in indoor plant cultivation, especially for cannabis. Two of the most well-known technologies are LED (Light Emitting Diodes) and HPS (High-Pressure Sodium Lamps). Both have their advantages and disadvantages, but which one is the better choice for ambitious growers? In this comprehensive guide, we analyze light quality, efficiency, costs, heat development, and yield.

1. Light Quality and Spectrum: How Important is the Right Light?

High-Pressure Sodium Lamps (HPS)

HPS lamps have been successfully used in plant cultivation for decades. They mainly come in two variants:

• Metal Halide (MH) – emits a bluish spectrum, ideal for the vegetative stage.

• High-Pressure Sodium (HPS) – emits a reddish-yellow light, which promotes flowering.

Disadvantages of HPS:

• The spectrum is not adjustable and lacks optimal UV and IR wavelengths.

• Light intensity decreases over time, requiring frequent lamp replacements.

LED Technology: The Modern Grow Light

Modern LED panels provide a full spectrum light that covers various wavelengths and can be adjusted individually. Advantages:

• LEDs emit blue light for the vegetative stage and red light for flowering.

• Many LED panels feature integrated UV and infrared light, enhancing resin production and plant metabolism.

• Light output remains consistently high for many years.

Conclusion: LED lights offer an optimized spectrum with better adaptability and higher PAR values (photosynthetically active radiation).

2. Energy Efficiency: How Much Power Do LED vs. HPS Consume?

Energy Consumption of HPS

• A 600W HPS lamp consumes about 660W including the ballast.

• A significant portion of the energy is converted into heat, not usable light.

• Light efficiency: around 1.4 µmol/J.

LED: More Light with Less Power

• A modern 300W LED lamp can replace a 600W HPS lamp while consuming only 50% of the energy.

• LEDs have high efficiency, with a light output of 2.5 to 3.0 µmol/J.

Conclusion: LED technology saves energy costs in the long run and offers a higher light output per watt.

3. Heat Development: How Does Lighting Affect the Climate?

Heat Issues with HPS

• HPS and MH lamps generate a lot of heat, which can lead to temperature problems in the grow room.

• The need for a strong exhaust system and possibly additional air conditioning.

LED: Less Heat Generation

• LED lamps produce 50-70% less heat than HPS lamps.

• This keeps the climate in the grow room more stable, reducing the need for cooling.

Conclusion: LEDs reduce cooling requirements and help maintain stable temperatures in the grow space.

4. Cost of Purchase vs. Operating Costs

HPS: Cheap Purchase, High Running Costs

• 600W HPS complete sets cost 100-150€.

• Bulb replacement every 9-12 months required.

• High electricity costs, especially with multiple lamps.

LED: Higher Investment, Long-Term Savings

• High-quality LED panels cost 300-1000€.

• Lifetime: up to 50,000 hours.

• No bulb replacements needed, low maintenance costs.

Conclusion: LEDs have a higher upfront cost but save money over time due to lower electricity and maintenance costs.

5. Yield and Quality of Harvest

HPS Yield

• HPS lamps provide high yields, but often with less resin production.

• Lack of UV and IR light may limit terpene and cannabinoid production.

LED: Maximizing Yield and Potency

• LEDs can achieve similar or higher yields than HPS lamps.

• More resin production and enhanced aroma, due to integrated UV and IR wavelengths.

Conclusion: LEDs allow for higher quality buds and improved resin production.