The Ultimate Guide to LED Grow Lights

While there are many types of hydroponic lighting, there’s a lot of talk in the hydroponics world about LED grow lights and how they just might be the “next big thing” in indoor garden lighting. Like a lot of products in the hydroponic market, there is a lot of marketing and hype behind LEDs.

Sometimes it’s hard to know for sure if LEDs are a good solution for your garden when you’re slathered in marketing and the anecdotal evidence of hydroponic growers online. To solve this, I decided to take an in-depth look at what’s REALLY going on with LEDs in an impartial manner. Let’s get started with the advantages of LEDs over other lighting technologies!

The Advantages of LED Lighting

Let’s take hydroponics out of the equation for a second and just look at the advantages of LEDs when compared to incandescent and fluorescent bulbs. After we understand the general advantages we can then apply those to hydroponics and see if they still hold.

The short list:

  • Less energy
  • Last longer
  • Smaller
  • Solid state (more durable)
  • Lower heat

Along with these basic advantages, LED lighting also has a high luminous efficiency when compared to incandescent and fluorescent lights. Luminous efficiency is the ability of a light source to produce visible light, so the more efficient a light source is, the more visible light it produces per unit of power input.

Something to keep in mind before reading on is that more visible light does not always mean better.

Read more about Photosynthetically Available Radiation to see why.

LEDs can reach 18-22 lumens per watt, while incandescent bulbs reach 15 lumens per watt for a 60-100 watt bulb. Fluorescent bulbs reach 100 lumens per watt. While it looks like fluorescent bulbs are outperforming LEDs, it’s been shown that LEDs are roughly following Moore’s Law, meaning that their lumen per watt output is roughly doubling every 18 months.

LEDs Last Longer

LEDs last far longer than incandescent or fluorescent bulbs. There are reports of LEDs manufactured in the 70s and 80s that are still working today! This is because they are solid state, meaning that there are no vacuum or gas components. LEDs can last anywhere from 25,000 to 100,000 hours before they are expected to fail.

They are Heat Efficient

Another benefit to LEDs is their heat efficiency. Unlike high pressure sodium bulbs, they do not emit a lot of heat into the growing environment. Because air and water temperature are so important to a hydroponic grow, this could be a massive benefit for those that are growing in confined spaces or need to control their heat for other reasons. It also allows you to place your lights much closer to your plants’ leaves, which helps you take advantage of the inverse square law for light.

Control Over Color Temperature

Color Spectrum of Average HPS Light

Color Spectrum of Average HPS Light – mostly in the green/red area

A huge potential benefit to using LEDs is their ability to be customized to any color temperature for growing. As I’m sure you all know, plants need different colors of light in different phases of growth. Often times you need to buy two different types of CFLs in order to satisfy a plant’s lighting needs throughout it’s entire lifespan. If you go the high pressure sodium route, it’s often only viable for flowering because of its heavy focus on the red area of the spectrum, which is used in the flowering or fruiting phase.

With LEDs, you could theoretically buy a system that has color filters on sets of individual LEDs for each area of the light spectrum that a plant needs. Then you could adjust the amount of each color that is on at any time to perfectly customize the color spectrum to your plant’s exact needs. There are some systems out there that exist like this, but they are few and far between and the ones that do exist are fairly expensive. If you want to spare no expense with your grow, you might want to look into this further.

Disadvantages of LEDs for Hydroponics

Cost

Right now, quality LEDs are very expensive when compared to other types of lighting for hydroponics. We’re talking about $400 for a 150 watt system from a reputable supplier versus $99 for a 1,000 watt HPS and another $200 for the ballast. The price of LEDs is expected to drop significantly in the next 2-3 years, so be on the lookout for very affordable LED systems in the future.

Plant Growth Results

There’s been a lot of chatter on various forums, blogs, and other grow journals about lackluster results from LEDs as far as plant growth goes. The “claim” by LED companies (and there are many) is that a 300w LED system is equivalent to a 600w-1000w HPS setup, but the evidence is suggesting otherwise. While many people are finding them good for the vegetative phase of most plants, most are not seeing great yields if they take their plants to flower using LED panels. There have been some experiments where even a T5 CFL setup outperformed LED panels for vegetative-only plants like basil, lettuce, etc.

Want To Try LEDs? Here are Some Ideas

The jury seems to be in: LEDs are an emerging grow light technology with some really exciting applications in the future. They ARE effective now, but they’re probably not the best lighting choice to bring a plant from seed to harvest with because of their lower yields and high cost to get started. To match the yield you could get using a HPS, you’d probably have to invest in the same amount of wattage of LED panels,which would be at least twice as expensive. However, it would be less expensive in the long run when you consider the lower electricity expense you would be incurring, along with lower costs for dealing with the heat that a HPS puts out.

LEDs have the potential to outpace HPS, Metal Halide, and CFL lighting solutions in the coming years, but for a hobbyist right now they’re just a bit expensive to use throughout an entire grow cycle.

If you do want to mess around with them and not break the bank…here are some ideas:

  1. Use them as a supplemental grow light for some extra light output for relatively low head and cost (excluding purchasing cost)
  2. Use them for plants that do not flower (lettuce, basil, most herbs)
  3. Use them for plants that do flower, but only for the vegetative phase. Then switch to more powerful lighting

I hope this was a helpful guide for anyone considering LED lighting. If you have any questions, comments, or think that I missed something (I probably did!) then please leave a comment:)

  • Nice article Kevin!
    I have also been reading on led lights, but the fact that lets me think they will be huge deal in the future is that you can take only that spectrum diodes that your plants need so they have great PAR rating and it does not matter that much that they have a lower lumen output than HID lights.

    • Kevin

      Hey thanks Midowo!

  • Pedro

    I dont know the date of this article, but the given figures are very outdated. LEDs can easily achieve efficiencies in the range of 100 lumen per watt. In fact, there are lots of 120 lumen per watt LEDs, but as always, there are losses in the drivers, and all other components of the system that make 120 lumen per watt a little bit hard to achieve. But 100 lumen per watt is definitely achievable.

    The future… is already here…

    • I wrote this one a while back Pedro – you’re right. LEDs are improving REALLY fast – I actually have a setup I’ve been using to pretty good effect. Would love to hear more about your setup!

  • Brikan

    LED grow lights are absolutely a wonderful thing.And these products helps in indoor and greenhouse use Top LED Grow Lights for growing Plants, food, medicine and More.

  • Brikan

    LED grow lights are absolutely a wonderful thing.And these products helps in indoor and greenhouse use Top LED Grow Lights for growing Plants, food, medicine and More.

  • Neil Malte

    How high should i place my led lights from my basil plants? I am growing in a nft system and i was wondering what heights i should do for the different stages of growth. Great article and thanks for the help.

    • For LEDs, best rule is “as close as possible.” They run cool so you can afford to put them very close, just as long as you actually get full coverage on your plants.

  • Kim Greenlee

    I have a foody garden tower. Last year I attempted my first grow. I gre broccoli, cauliflower, cabbage, Brussels sprouts, and Swiss chard – indoors. I used a gro light from Amazon to sprout and then used two of the same gro lights (floureacent) on the plants once they went in to the foody (vertically). They never produced any vegetables. Just awesome vegetation. I think they needed more of the red spectrum as the two bulbs I had were full spectrum but heavy on the blue. My question is. Should I add another flourescent with more red spectrum to the mix to get them to produce this time? How do I know how much to give them? Or should I use an led and how much do I need. My tower is about 5 feet tall and 1 -2 feet wide. I keep searching to find the answers but haven’t found them yet

    • Yeah, it’s very hard to grow things like broccoli on simple grow lights, especially if you’re growing vertically. Better to put out in the sun.

      A good rule of thumb is if it flowers (like broccoli), it needs a LOT more light, and especially red light. Not impossible to grow with LEDs or indoor lighting, but you need quite a bit of wattage. A 400w HPS would do well, and you’d have to switch to more red light the closer the plant came to setting fruit.

      I would personally grow leafy greens in a vertical tower because they require less light and do not flower, meaning you can use a cool blue LED light setup and they will flourish. I’d save the broccoli for at least a horizontal setup, but likely just use an outdoor hydroponics system.

  • Don Arnold

    When was this document written

    • A while ago, but I am working on an updated version for 2016-2017 🙂

  • Judy Wilson

    Knowing how to take advantage of the inverse square law for light in hydroponic growing seems really important. It’s great that LED growth lights can do this by being more eat efficient. I’ve been having trouble controlling the heat in my air and water temperature since my plants are in a really confined space, so maybe LED growth lights are the answer.
    http://healthyhydro.com/hydroponics/

  • combizs

    any recommendation on what LED setup to buy for growing lettuce and/or basil with an indoor hydroponic setup?

    • Lettuce and basil? I would recommend more blue than red light there, as they don’t flower and plants use more blue light during the vegetative phase of growth. As far as specific recommendations, I don’t feel comfy recommending yet as I’m still doing research on the best LED lights. But stay tuned!

  • littlekitfox

    I’m just a super beginner for growing indoor. Would like to grow microgreens, baby lettuce and herbs, and also starts for my (outdoor) garden to get a jump on the season. Going to hang the lights on a metal wire rack. Suggestions for LED vs T5, given current info and LED options?

  • Thomas

    OK. I may be asking a crazy question, but here goes. I have so much shade in my front yard that we can’t grow anything but high shade tolerant plants. That’s fine for part of the yard, but for curb appeal we’d like some flowers in built in planters up next to the house. We also need lighting around the house, since it’s very dark at night… So I’m wondering about doing “under eave” recessed lights and putting LED??? grow lights over those planters. Is that crazy, and would the light color just look weird at night? They would need to be 6 ft above the planter box. I think I can get a solid 8 hours of night, with plenty of dark time for the plants, too.