LED vs. CMH Grow Light Cost Comparison

LED grow lights are a bargain in the long run compared with ceramic metal halide lights and fixtures. That may be shocking when you shop for LED fixtures, which cost considerably more than CMH fixtures to buy.

For the total picture, look at all the costs—not just purchase costs but also electrical costs and bulb replacement costs. Over the long haul, you will have saved money with LEDs as opposed to CMH lights.

Costs aren’t everything; lights have to be effective. Both LED and CMH grow lights are effective for every phase of your plants’ life.Typically with LED fixtures, you can adjust the light spectrum your plants are getting, increasing blues and/or reds for flowering and budding. With a CMH grow light, you must replace the bulbs for more blue or red, adding cost. But CMH lights are famous for strong harvests with big flowers and heavy, full buds.

Look at all the factors, then decide which light is right for you.

Purchase Price

Do LED lights cost more than CMH lights? Yes! You’ll spend as much as 80 percent upfront more to buy an LED grow light than a CMH fixture.

The average LED light fixture at GrowersHouse, including the lights, is roughly $775. That includes high-end commercial fixtures that can top $2,700; hobbyist-grade lights as low as about $96; and many lights in between.

By contrast, the average price of a CMH fixture from GrowersHouse is just a bit over half as much, at less than $425, including the CMH bulb or bulbs. CMH fixtures also have a tighter price range, from about $82 for the least expensive hobbyist setup on our site to about $735 for the highest-priced commercial-grade fixture.

You would have to make up about $350 per fixture in operational savings over the lifetime of the fixture to make the LEDs pay for themselves, but such savings—more, actually—are entirely likely over years of use.

Electricity Savings

Do LED grow lights help you save on energy? Yes. Spending less on energy by using LEDs instead of CMH lights comes in two ways:

  • LEDs give off more usable light at similar or lower wattage, saving 15 percent on average.
  • LEDs emit less heat, so the cost of air conditioning, air flow and dehumidification can be lower, with results varying by location.

Calculating at the average U.S. electrical cost of 13.19 cents per kilowatt hour, a 640-watt CMH light burning 12 hours a day for a month costs $30.39 to operate. An LED, which generally uses 15 percent less electricity, would cost about $25.83 a month to run, a savings of $4.56 per month. In a year, the minimal electrical savings from the LED fixture alone would total at least $54.72. If you keep your LED fixture for just five years, the warranty period for most quality LED grow flights, that’s a savings of $273.60. In 10 years—it’s plausible that an LED fixture would last that long—the electrical savings would be $547.20. The five-year electrical savings just about makes up the difference in purchase price for the LED, and the 10-year savings more than covers it.

Potentially the electrical bill savings could be even higher. That’s because LEDs tend to generate a higher PPF per watt, so a lower-wattage LED could replace a higher wattage CMH with equal or better results in growing and flowering. One lighting manufacturer, for example, got a usable PPF output of 530 from a 241-watt LED versus 439 usable PPFs from a 340-watt CMH. The energy savings over 3 years in that locale was 42 percent, or $888 for the LED compared with $1,515 for the CMH. An owner would recover the $119 premium to buy the LED fixture several times over on electrical savings alone.

Additional savings on electrical costs are difficult to quantify because of variables, but that same manufacturer found that its LED fixture, while emitting more usable light, cast off only 20 percent as much heat as the CMH did. A scientific study in California by the Emerging Technologies Coordinating Council found that using LED fixtures versus HPS lights, which burn hotter than CMH bulbs, saved 2 percent on a/c and dehumidifying costs. So, the potential exists for saving on temperature and humidity control with LED instead of CMH, perhaps just not as much as compared with HPS.

Don’t doubt that LEDs can generate higher PPFs on fewer watts. In the ETCC study, two crops under LED fixtures actually suffered poor starts from burns because the grower underestimated the additional PPFs coming from the LED fixtures. With another grower, however, crop results under LEDs were normal or better with a 35 percent savings in fixture electrical costs and a 2 percent savings in a/c and dehumidifying costs.

Longevity and Bulb Replacement

Fixtures can last a long time, so let’s compare bulb replacement costs over 10 years.

CMH lighting requires frequent bulb replacements and changes:

  • Annual replacement of the CMH bulb, or two if you have a dual fixture.
  • Replacement of 4100K CMH bulbs used in the vegetative phase with 3100K CMH bulbs for flowering, then back to the original 4100K.

CMH bulbs typically are replaced every year, not because they no longer light up but because they emit significantly fewer usable PPFs after a year—probably 10 percent less. They generally are rated to have a 20,000-hour lifespan, but at that point their light output would have degraded perhaps 40 percent or more—about 10 percent a year.

The price of a CMH bulb averages about $75, so you’ll have at least that replacement cost annually. If your fixture has two lamps, the yearly replacement figure jumps to $150. That means that on one fixture over 10 years, you’ll have an additional $750 to $1,500 for lamp replacement alone. If you want to change the blue or red output on a CMH fixture, you also must replace the lamps for budding/flowering once a year, so add another $75 to $150 a year, or another $750 to $1,500 over 10 years. That means that over a 10-year period, you’re now at $1,500 to $3,000 just for lamp replacements and changeouts on one CMH fixture.

LEDs are clearly the winner on replacement costs. LEDs do not require an annual replacement. These low-heat lights are considered to have a lifespan of 50,000 to 100,000 hours. If you burn LEDs 12 hours a day for a year, that’s 4,380 hours. At that rate, a light that lasts 50,000 hours would function for 11 years. Because the spectrum on LEDs is adjustable, substitute bulbs for flowering aren’t necessary, either.

The light emitted by LEDs degrades a fraction as fast as the light from a CMH bulb. Expect LEDs to lose about 1.4 percent of their effectiveness each year. So, after 10 years, your LED fixture should be emitting 86 percent of its original light level—giving more of its original light than a CMH bulb would after just two years. Most quality LED fixtures are warranted for five years, so your maintenance costs are likely to be nil for that time. Can LEDs or drivers go bad? Of course, but LEDs have undergone decades of development, even though LED grow lights are relatively new. The simplicity of LEDs helps make them ultra-reliable.

You may want to hold onto an old MH or HPS fixture or two in case an LED does need repairs, which probably would require you to ship the fixture for repairs. You could use an old fixture while the LED light is being repaired. An alternative strategy is to buy LED fixtures with removable, replaceable LED diodes. The only problem is that, for now, such fixtures cost even more than other LED lamps.

Conclusion: LEDs Save Big Over Time!

The evidence says LEDs are cheaper than CMH the longer you keep them. But all budgets vary, and if yours says go for cheap but effective to start, CMH lamps will cost you less up front. You’ll pay more every month for energy, but if that’s more doable than shelling out for higher-cost LED fixtures up front or borrowing with interest to purchase them, go with CMH.

See Our LED Testing Results

Want to see how the LED lights that we sell are stacking up against each other? Check out our data and comparisons below!

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