How to Compare Grow Lights (LED vs HPS, MH)

How to Compare Grow Lights (LED vs HPS, MH)

As technology improves and evolves, old systems and tools become outdated.  They are often replaced by newer, more efficient technologies that do a better job of achieving the results they are intended to produce.  So it goes with grow lights and horticulture lighting systems. Where growers once relied on the raw, inexpensive output of High Pressure Sodium (HPS) & Metal Halide (MH) HPS or MH lights, the advances in LED lighting technology have won a vast majority of the horticulture industry over to the LED revolution. 

So, how does a grower compare grow lights, particularly LED vs HPS?

LED Grow Lights vs HPS Grow Lights

HPS & MH fixtures have long been the go-to technology for industrial lighting, like warehouses and factories. Sodium lamp technology originated in the 1930s and works by creating an electric arc through vaporized sodium metal. Other gases have been used to varying degrees over the years to start the lamp and control the color of the light output. The disadvantages of HPS fixtures are obvious, given that they rely on pressurized bulbs full of gas.

Not only is the technology for HPS & MH outdated, environmentally unfriendly, and inefficient, they are also risky for cultivators investing in large scale indoor crop production.  They tend to fail more frequently and degrade much faster than Light Emitting Diodes (LED). In addition they are not as easy to adjust or control. Most importantly, they drain a tremendous amount of unused electricity and subsequently produce a lot more heat.

When every watt counts, especially in industrial size grow warehouses, LED becomes immediately more attractive as the more energy-efficient alternative. LED grow lights allow for a high degree of customization in the color spectrum as well.  While HPS & MH lights often put out substantially more raw intensity, they don’t contain large amounts of photosynthetically active radiation necessary to stimulate plant growth. That’s why many growers who rely on HPS in the flowering stages & MH for the veg stage are forced to supplement with HID (High Intensity Discharge) lights of a different spectrum and configuration in the veg rooms, increasing the overall cost of the lighting investment.

Factors to Consider when Comparing LED vs HPS Grow Lights

It’s important to remember that you’re not just buying watts when you invest in grow lighting. Electricity does not grow plants. The important metric is the amount of plant nutrition or PAR that comes out of those lights.  Certainly the best LED grow lights produce maximum PAR with fewer joules of electrical input, calculated as photon efficacy.

Spectrum is often lauded by lighting manufacturers of all stripes as the differentiating factor for their fixtures. Keep in mind, however, that plants respond to the full spectrum of PAR, meaning the 400-700nm range. While there are certainly impressive custom configurations for spectrum emerging in the market, no one company has a “magical spectrum” that will overrule the need for suitable PAR levels and even PPFD distribution.

That brings us to the importance of PPFD. The amount of PAR landing on the canopy of the plants is calculated in PPFD, but don’t be fooled by aggregate numbers here. You want to make sure the PPFD levels are uniform across the entire growing area by seeing a variety of measurements and then determining the mean.

LED Grow Lighting is the New Standard

While HPS and other forms of lighting have had their day, LED is here to stay. With advances in diode configuration, color spectrum, thermal management, and advanced directional optics, today’s LED grow lights are vastly outperforming the clunky chemical technology of High Pressure Sodium lighting.  With the cost of LED fixtures dropping substantially in recent years, the newer tech is more accessible than ever.


Explore the SpecGrade LED line of advanced grow lighting and learn why today’s professional cultivators are relying more and more on our state-of-the-art LED grow lights.