Transitioning from HPS to LED Grow Lights
The shift from high-pressure sodium (HPS) to LED grow lights marks a pivotal change in indoor horticulture, driven by advancements in lighting efficiency, spectrum control, and affordability. While most cultivators now rely on LEDs, some maintain hybrid HPS-LED systems or stick with HPS due to established practices yielding consistent results. However, LEDs’ reduced heat, custom spectrums, lower operational costs and better quality yield make the transition increasingly compelling sustainability. Building on NOKOTECH’s Choosing LED Grow Lights guide, this article explores the evolution of this shift, its benefits, economic impacts, and critical adjustments – such as nutrient EC levels and HVAC – to ensure a smooth transition.
The Evolution of the Transition: From Early Adoption to Industry Standard
The adoption of LED grow lights began around 2010 due to consumer availability, primarily among small-scale hobbyists in warmer regions like southern Spain and the southwestern United States, where HPS’s high heat output (up to 700°C bulb surface temperature) posed challenges for small grow spaces. Early LEDs offered lower heat but lagged in spectrum quality and photosynthetic photon flux (PPF), making HPS the go-to for reliable yields.
Over the past five years, LED technology has advanced significantly. Modern chips achieve efficacies of 2.7–3.2 µmol/J, with customizable spectrums and higher PPF. The LED grow light market, valued at $3.86 billion in 2024, is projected to reach $4.8 billion in 2025, growing at a 24.4% CAGR. While some cultivators remain loyal to HPS for its predictable performance, affordable options like NOKOTECH’s Simplex PRO or Simplex MAXI-FIT (2.8 µmol/J) facilitate broader adoption.
Key Benefits of Switching to LEDs
LEDs outperform HPS in several critical areas, transforming indoor cultivation:
- Spectrum Customization: LEDs deliver a balanced full spectrum, rich in blue (400-500 nm), red (600-700 nm), and sometimes far-red (>700 nm) wavelengths, unlike HPS’s yellow-orange-heavy output. This enhances the Emerson effect, boosting photosynthesis efficiency by 20-30% in some crops, resulting in stronger plants and higher yields.
- Optional UV add-ons (UVA 315-400 nm, UVB 280-315 nm) stimulate flavonoids and anthocyanins, improving pest resistance and flavor profiles in herbs and fruits.
- Energy Efficiency: LEDs use >40% less power than HPS for equivalent light output, with efficacies of 2.6 – 3.1 µmol/J compared to HPS’s 1.5 – 2.0 µmol/J.
- Reduced Heat: Lower heat emissions reduce cooling costs and plant stress.
- Longevity and Safety: LEDs last over 50,000 hours with minimal degradation, compared to around 10,000 hours for HPS, and offer higher water resistance and easier installation.
Products like NOKOTECH’s Simplex PRO and Undercover 150 (300W, 836 µmol/s PPF with far-red) provide cost-effective, high-performance solutions tailored to diverse grow setups.
| Benefits of LEDs over HPS | Details |
|---|---|
| Spectrum Customization 🌈 | Balanced wavelengths enhance photosynthesis and overall plant health. |
| Energy Efficiency 💡 | Up to 90% less power consumption; higher µmol/J ratings. |
| Reduced Heat ❄️ | Minimizes cooling needs and plant stress. |
| Longevity ⏳ | 50,000+ hours with stable performance. |
| UV Integration ☀️ | Improves pest resistance and crop quality. |
| Safety and Ease 🛡️ | Water-resistant; straightforward setup. |
Environmental Sustainability: A Key Advantage
LEDs reduce environmental impact significantly. Unlike HPS, which contains mercury requiring controlled disposal, LEDs are toxin-free. Their 50,000+ hour lifespan cuts replacement frequency, lowering manufacturing and transport emissions. Energy savings of 40-60% reduce carbon footprints, potentially cutting energy demand by 10-25%. This aligns with sustainable practices for indoor growers aiming for eco-friendly operations.
Economic Analysis: Electricity Savings, ROI, and Yield Comparisons
Energy savings are a primary driver for transitioning to LEDs. Consider a mid-sized setup with four 600W LEDs (total 2,400W) versus four 1,000W HPS (total 4,000W). Operating 12 hours daily during the flowering stage, LEDs consume 28.8 kWh per day, while HPS uses 48 kWh. Annually, this translates to 10,512 kWh for LEDs and 17,520 kWh for HPS.
At the UK’s average electricity rate of 26.35p per kWh (October-December 2025), LEDs cost approximately £2,770 per year, while HPS costs £4,616, yielding annual savings of £1,846 (excluding daily standing charges of 53.68p). For larger operations, savings can reach millions over five years. Additionally, LEDs can increase yield quality and quantity by 20-50%, further enhancing ROI. For example, 600W LEDs often match or exceed the output of 1,000W HPS, with improved density and potency.
Nutrient Adjustments: Do LEDs Require Higher EC?
LEDs reduce transpiration, concentrating nutrients and often requiring a 0.1–0.3 mS/cm higher EC (e.g., 1.3–2.3 mS/cm vegetative, 2.0–2.8 mS/cm flowering). Boost Ca/Mg by 10-15% to support blue light-driven growth. Monitor pH (5.8–6.4) weekly to prevent deficiencies or toxicities.
HVAC Considerations: Recalibrating for LEDs
Switching to LEDs significantly alters HVAC requirements due to reduced heat output. HPS’s high radiant heat (up to 700°C bulb surface) contributes to grow room warmth, often requiring robust cooling systems like air conditioners to maintain 20-28°C. LEDs generate significantly less heat, shifting the HVAC load from cooling to heating and humidity control.
- Heating Needs: In cooler climates, LEDs lower leaf surface temperatures (LST) by 2-4°C, requiring ambient temperatures to rise to maintain LST at 23-25°C. Supplemental heaters (e.g., 1-2 kW electric units for a 4x4m room) may be necessary, especially in winter, increasing costs upfront. Use infrared thermometers to monitor LST and avoid cold stress.
- Cooling Reduction: LEDs significantly reduce cooling, allowing smaller AC units or fewer fans. This can save energy costs, offsetting heater expenses.
- Humidity Management: When using LEDs instead of HPS, relative humidity (RH) increases by 5-10%, increasings risks of mold and other deseases. Dehumidifiers are critical when growing with LEDs. Maintain vapor pressure deficit (VPD) at 0.8-1.0 during vegetative stage and 1.0-1.5 kPa during flowering stage using VPD charts or VPD calculators.
- Ventilation Adjustments: LEDs require less aggressive exhaust to remove heat but need-consistent air exchange to prevent CO2 depletion (600-1,500 ppm optimal). Recalibrate fans and consider CO2 generators for high-intensity setups.
- HVAC Integration: Automated controllers unify heating, cooling, and dehumidification, costing £200-£500, but optimizing conditions.
Addressing Challenges in the Transition
The shift to LEDs introduces several environmental and operational adjustments:
- Temperature Control: Raise ambient temp to maintain LST at 24-25°C; use heaters and infrared thermometers. Below 22°C is considered cold stress → droopy leaves, slow growth ❄️. Above 28°C is considered heat stress → yellowing, burnt tips, minimum 20% yield loss 🔥
- Humidity Regulation: Humidify in veg stage to 65-70% RH if needed (usually, because electric heaters dries air) and Dehumidify in flowering stage to 50-58% RH. Track VPD at 1.0-1.5 kPa in flowering stage.
- Nutrient Calibration: Increase EC by 0.1–0.3 mS/cm; boost Ca/Mg 10-15%.
- Light Intensity: Hang LEDs at 30-45 cm; dim to 600-1,200 µmol/m²/s. Use PAR meter (very precise) or smartphone apps (less precise) to check the exact numbers.
- CO2 Integration: Supplement to 1,200-1,500 ppm for high-output.
Common mistakes to Avoid:
- Hanging Too High: LEDs allow 30-45 cm proximity.
- Overwatering: Less heat slows drying; adjust schedules.
Conclusion: Optimizing the Shift to LEDs
The progression toward LED dominance in indoor growing is supported by robust market growth and technological refinements, making now an ideal time for transition. With lines like NOKOTECH’s Simplex PRO, PRO-FIT, MAXI-FIT or Undercover 150 delivering efficient, spectrum-optimized solutions, cultivators can achieve superior yields and sustainability. For further discussion and resources, join the NOKOTECH Telegram club.
