LED vs. HPS Grow Lights: Which Is Better for Cannabis?

LED vs. HPS comes down to this: HPS lamps are cheap to buy and proven, while LEDs cost more up front but burn far less power and let you tune the light spectrum. For decades, high-pressure sodium (HPS) lamps were standard equipment in pretty much every indoor cannabis grow room, delivering fast growth and consistently big yields. But better-quality light-emitting diode (LED) fixtures have kicked off a debate over whether it's time for a total overhaul in cannabis lighting.

LEDs have always been far more energy-efficient than HPS, but for years that edge was overshadowed by how much more they cost to set up. But as the tech improves, prices keep dropping, and with recent research highlighting LEDs' potential to boost cannabinoid content in cannabis plants, plenty of growers are starting to think about making the switch.

Before grow rooms or “indoor grows” existed, cannabis grew wild outdoors, usually sprouting in spring and flowering in fall. You don't have to be a grower to know that each season has its own colors, with autumn sunlight turning golden as it washes over a landscape of reds and browns. That shift in light comes from the angle of the sun, which sits lower in fall than in summer, so more of the light reaching the plants falls in the longer wavelengths toward the red end of the spectrum.

When you grow cannabis indoors, the goal is usually to recreate the ideal natural conditions your plants need to grow big and pack on cannabinoid-rich buds. In practice, that usually means giving them plenty of red and far-red light during the flowering stage, typically in the 600 to 780 nanometer range.

Without getting too technical, it's worth knowing that HPS lamps use vaporized sodium to produce a strong orange glow, which sits at the long end of the spectrum and is excellent for flowering cannabis. That's usually boosted with a few other gases that add a wider range of wavelengths, giving a whiter light.

In the never-ending quest for perfection, some pioneering growers found that LEDs can actually deliver bigger yields and better-quality buds. That's because LEDs can be set up to emit specific colors of light, letting growers give their plants the exact wavelengths they need at each growth stage to push cannabinoid concentration as high as possible.

As we mentioned, the high cost of installing an LED array was a major turnoff for years, though these systems keep getting cheaper. On top of that, by some estimates, LED fixtures use somewhere between a quarter and half the energy of HPS lights, which can add up to massive savings over the long run.

Given that lighting can account for up to 85% of a typical grow room's energy use, switching to LED clearly brings real financial and environmental benefits.

That said, it takes a bit of tech know-how to get comfortable with LEDs, and rookie growers may find them a lot trickier to dial in than HPS. On the other hand, the old-school grower mindset is deeply attached to sodium, and some growers' lighting choices may have more to do with what they've always used than with trying something new.

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