Growing Plants Indoors with LED Grow Lights
Growing plants indoors using LED grow lights is one of the most popular topics today. However, only a small number of growers actually use LED lights, though this number is rapidly increasing every day. It’s no surprise that there are many questions about them, and people often wonder whether they are really better than HPS lights. Do they save money? Does the cost of installing LED lights offset high electricity bills? Can LEDs help summer plants bloom when needed? LEDs seem better for both your wallet and the environment, so why not compare LED and HPS lights? Many may find this hard to believe, but there are plenty of solid reasons to choose LEDs. Regardless of manufacturers’ exaggerated claims, there is a core truth I can point out.
The Issue
Indoor gardening is expensive and time-consuming. Artificial lighting can significantly drive up costs. After all, recreating July sunlight indoors is no easy task. Before the recent LED trend, HPS lights were the standard, and they were always power-hungry. Therefore, finding the most energy-efficient light that also produces more light has always been a race. Electronic ballasts were the first major improvement, providing more output at the same wattage—they changed the game. Today, LEDs promise twice the efficiency of adding ballasts. If they are that powerful, why haven’t they completely taken over indoor gardening yet?
The Results
Compared to HPS grow lights, LED grow lights excel in nearly every aspect, particularly in light intensity and heat output.
Light Intensity: Many people worry about the intensity LEDs can provide. Compared to HPS lights, light intensity is almost equivalent. What stands out is that LEDs outperform HPS in tests, even when they don’t seem to produce stronger light. In trials, LED grow lights consistently deliver uniform yields and suggest that future technology improvements could increase output further, especially when compared to HPS.
Heat: If you are using HPS lights and constantly battling heat, LEDs provide a remarkable advantage. Instead of spending extra money on air circulation and cooling to avoid burning plants, LEDs can almost touch plants without causing harm. Of course, if you are growing in cold conditions, HPS may still be useful, though sometimes it is easier to heat a grow room than risk using HPS lighting. LED grow lights may generate more heat as they scale up, but current models are warm to the touch and do not produce the intense heat of traditional grow lights.
Yield: LEDs have been tested repeatedly for yield. Generally, most indoor growers using HPS achieve about 0.5 g/watt. In comparison, LEDs often produce 1–1.5 g/watt, up to three times more efficient. Each harvest can yield three times the usual output.
Lifespan: Average HPS systems last about 10,000 hours—a long time for growing, but LEDs go much further. LED systems can last 50,000–100,000 hours. That’s equivalent to 15 YEARS of high-quality, cheaper, more efficient, and easier indoor growing. Many growers experiment with different red and blue combinations to achieve the perfect spectrum for their needs.
Flexibility: Compared to HPS, LEDs are far more flexible. HPS lights are bulky and limited in placement. LEDs, however, can be positioned around your plants and placed relatively close without producing excessive heat.
Light Spectrum: The light emitted by LEDs is specifically designed for flowering and vegetative growth stages. HPS lights emit the full spectrum, while LEDs focus on blue and red wavelengths that match plant needs, ensuring every photon is used efficiently for a specific growth stage.
Operating Costs of Grow Lights
Comparing the Performance of LED Grow Lights and HID Grow Lights
For comparison, we refer to an optimized HPS system with the following specifications:
- Digital ballast (95% efficiency)
- High PAR bulb (Sunmaster, Grow+ Photonic)
- High-quality reflector (Adjust-A-Wing Defender, medium size)
- Closed environment with highly reflective walls (silver mylar)
The performance of this system is 1.3 µmol/watt PPFD (photosynthetic photon flux density). This means that for every watt of energy consumed, 1.3 µmol of PAR light reaches the plant canopy.
Today’s LED grow lights can deliver nearly twice the PAR lighting efficiency to the canopy.
Comparing Operating Costs of HID and LED Grow Lights
Although the purchase cost of LED grow lights has decreased significantly in recent years, you still pay three to four times more for a high-performance LED grow light system compared to a high-performance HPS system.
However, by saving 48% on electricity and avoiding the cost of replacing bulbs, you can recoup your investment in less than a year. After that, you will save costs for every subsequent growing year.
Below is a cost comparison for providing an average PAR intensity of 800 µmol/m²/s in a 5ft x 5ft (1.5m x 1.5m) growing area.
To achieve this average PAR:
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High-performance LED grow light: 750 watts, operating cost $846 per year (14 hours/day at $0.23/kWh)
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HPS grow light: 1400 watts, operating cost $1,627 per year (14 hours/day at $0.23/kWh)
Cost of HPS bulbs: $100; 750-watt LED grow light: $700
Doubling Your Yield in Grams per Watt
If you weigh your dry herb yield and divide it by the power consumed by the grow lighting system (per hour), you get a figure in grams per watt. This is the best way to evaluate the performance of a grow light system.
Typically, an HPS system yields 0.4–0.5 grams per watt. A typical 600W HPS system: 640 watts x 0.4 grams = 240 grams per grow cycle.
With a high-performance LED system, you can double the yield per watt.
Growing More in the Same Space with LED Grow Lights
Because LED grow lights run cooler and more efficiently, you can achieve higher performance in your grow area compared to HPS systems.
For example, a 1000-watt dual-ended 400V Gavita HPS light in a 1.5m x 1.5m tent provides around 650 µmol/m²/s.
A 750-watt LED grow light in the same tent provides an average PAR intensity of approximately 800 µmol/m²/s.
This 23% increase in average PAR intensity can increase crop yield by 23% while consuming 30% less electricity.
LEDs Provide the Optimal Spectrum for Short-Day and Dense Crops
HPS spectrum is mostly red and green. Red supports flowering, and green penetrates the canopy well. However, only a small amount of blue light (3–4%) is emitted, even in “dual spectrum” HPS bulbs.
This is why growers often use Metal Halide bulbs during the vegetative stage and why plants tend to stretch when switching to HPS for flowering.
Plants need 10–15% blue light to maintain growth density, and LED grow lights provide this ratio in their emission spectrum.
LED grow lights can be used for all growth stages without switching from vegetative to flowering stages.
Reducing Electricity Use by 40% and Heat Output by Switching from HID to LED Grow Lights
Modern LED grow lights are twice as efficient as optimized HPS systems, meaning you can reduce electricity use by up to 50% while maintaining the same yield.
Upgrade from HPS to LED and Reduce Heat Output by 60%
Inefficient grow light systems produce less light and more heat. Excess heat requires more ventilation, stressing and potentially damaging plants. In extreme cases, you may need to stop growing during hot weather or use air conditioning.
LED grow lights emit 60% less heat than equivalent HPS systems. Your plants will experience less stress in warm conditions, and your fans will run slower and quieter.
Saving with Rebates
Utility companies offer rebates for growers using approved LED grow lights. HPS lights do not qualify because they consume significantly more electricity. Utilities aim to promote energy-saving measures and encourage people to switch to LED lights through rebates.
Conclusion
LED Grow Lights vs. HPS Grow Lights: There’s not much debate needed—looking at the aspects discussed above, there’s no doubt that LED grow lights outperform current HPS lights. Of course, some people still trust their old HPS systems and have been very successful, but if you can afford it, making the switch is entirely worthwhile. Higher efficiency, effectiveness, and product quality are easily achieved with these lighting systems.
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