Compact Fluorescent Grow Light


Spring is on the way for our friends down under. With that in mind [x2Jiggy] built this compact fluorescent grow lamp to help start the seeds for his garden. He used materials that are easy to find, and multiple bulbs means that you can mix and match their color warmth in order to get the wavelengths of light best for plant growth.

He started by building the box out of MDF. It is lined mostly with a reflector meant to go in your car’s windshield when you leave it in a hot parking lot. He sealed the seams of the reflector using what he calls flashing tape. This is the rubbery type of stuff used as soft flashing around windows.

The bulb sockets came from an old string of party lights. Wiring is run through plastic junction boxes which keeps the setup code-compliant. Each of the CFLs draw 20 Watts for a total consumption of 160 Watts. Combine this with a DIY hydroponic tent and you’ll be eating fresh greens year round.

34 thoughts on “Compact Fluorescent Grow Light

      1. Not really, I bought all the LEDs I needed for something similar for under $15 on eBay. Each CFL must cost at least $8, so the CFL setup is much more expensive in terms of power consumption, build cost, and maintenance cost.

        1. Yeah, figures please or it didn’t happen! What LEDs were they? what was the forward voltage, max current, colour temperature? How did you power/cool/mount them? If you can find a decent LED *with* a power supply and adequate heatsinking and ventilation for the price of a cfl then please educate us!!

            Okay so it’s 2 years ago but maybe still a touch out of date.

            Even though LEDs are more efficient in the high end the general ones you find in the ‘bulb’ type “plug’n’play” lamps are not amazing in the lumens/watt range and are hideously expensive!
            Top shopping link from google

            A quick look at the datatsheet tells me this is only putting out 470 lumens for 8 watts, a measly 58.75 lumens per watt. I have cited an LED diode in reply to a comment below that claims 120 lm/w but it will require power supply, heatsink, etc and it only puts out 6 or 7 w (depending on the model you choose) hence needing multiple of everything. I could probably do just as well with any decent cfl bulb and still save a lot of money and time.

          2. Don’t get me wrong, I’m a massive high power LED and lighting enthusiast and I’m just as eager to see the next bitchin’ monster LED growlight, torch, flood or whatever hack but the realist in me says that if you’re skint and quick’n’dirty will do just fine (and if you’re here, it should!) then you can’t really do much better than this. Great hack! :)

    1. Members of our orchid society have done experiments with various forms of lighting. Red and blue LEDs sound like a good idea, so we tried them. Turns out their spectra are so narrow that the plants are deprived of some necessary wavelengths, and the plants grow stunted and deformed.

      The point at which LEDs become more economical than CFLs depends on the cost of electricity, how quickly it can offset the higher cost of the LEDs, and the effective life of the lamps. It’s very much not a straight forward computation.

        1. Just to be clear, we have had great success using “white” LEDs for growing plants. I use 145W floodlights from Aeon Lighting Technology that produce “neutral white” light. They consume less than half the power that High Pressure Sodium lights, and so produce much less heat, making them far safer. The LEDs produce less light per watt, but their light is in a much more plant-effective spectrum than the HPS, so the LEDs remain economical. The experiments were using Aeon’s own floodlights sold as “grow lights” that have red and blue chips, and they simply didn’t produce healthy plants.

          1. I’m pretty sure, whilst researching Cree XML’s and other high output LED’s I read somewhere that a massive factor in the ability for a diode to ‘throw’ it’s light properly has to do with it’s ‘surface brightness’ which if I understood it correctly has to do with it’s emitting surface output in relation to it’s die size.

            I’m not sure what the output of a modern HPS is but I am thinking of picking up a couple of these tomorrow.



            They claim 120 lumens/watt @ 300mA — 420mA max. lol 420, sounds like it was made for it. 6500K & 3000K temps. Any thoughts?

          2. @ColdTurkey, the data sheets show a half angle of 140 degrees, so they’re going to spread the light fairly widely. That means they’ll have to be slightly closer to the plant leaves. They’re certainly a good price, but you’ll need a decent power supply to pair with them. Make sure you have these mounted to adequate heat sinks, too. As far as color temperature goes, it depends on what you’re growing. If it’s just veggies and in a room you aren’t in, choose the color that produces the most lumens per watt. Because we grow orchids for their beauty and want to see them in a good light, I chose “natural white” as a compromise between the attractive “warm white” and the more efficient but cold blue “true white” choices.

      1. Using a mix of “red” and “blue” LEDS to grow plants is possible but you need exactly the right spectrum. It’s very energy efficient if you do it right – but as you pointed out, the emission spectrum of an LED is very narrow so it has to be right to within 10-20 nm.

        White LEDs are actually blue LEDs with phosphors that reduce the energy content of some photons to make different colors of light, which gives them an emission spectrum more like that of a fluorescent light. The downside is lower energy efficiency (all the photons are initially high-energy blue ones, which requires a larger band gap in the diode and therefore a larger forward voltage). However they are plug-and-play in the sense that just about any white LED will grow plants.

        I think LEDs would have been better just because CFLs lose lumens very fast – 50% in 3 months of 16 hours a day.

        Source: I’m an indoor plant hobbyist.

        1. @Nick, it may be “possible” to use red and blue LEDs, but as we found it wasn’t very effective, even with fixtures specifically marketed as “LED grow floodlights”. Plus, the purple glow was essentially an “evil” color, and made working with the plants nauseating. Orchid flowers have no beauty under those lights.

          We expect 50,000 hours out of our LED fixtures before the light output drops to about 60-70%, compared to just a few thousand hours of life in a fluorescent bulb before it hits 50%. Bulb cost is certainly a part of the savings.

          Because the light output is slightly less than the 400W HPS, we run the 145W LED fixtures more hours per day. Right now they’re on for about 15 hours per day, but we vary them from 18 hours over the summer solstice to about 13 hours for the winter solstice.

          HPS are still really effective, though. The lumens-per-watt ratio is almost comparable to LEDs (although the greenish-gold spectrum is largely wasted on plants), the bulbs last 25,000 hours and operate on vapor so they’re not as fragile as filament based bulbs, and are much cheaper than LED fixtures. But they’re so hot I’d consider them only for an outdoor greenhouse, business, or detached garage. I would never again risk placing one inside a home.

      2. White LEDs use a phosphor coating like CFLs to convert and spread the blue from the LED chip into light across the visible spectrum. Given the quickly dropping cost of high power mains-powered white LED modules, you might want to repeat your experiment with some of those.

  1. He would be better of using flat white paint than those wrinkled reflectors. Flat white paint has been shown in many trials to be better than aluminized surfaces, especially if the aluminized surfaces are wrinkled. Mylar would be best though, if it was positioned with precision to reflect the light in the most efficient path (not back into the bulbs etc). Flat white paint reflects light in a more diffuse manner which is the most efficient with simple reflector designs like this. And flat white paint is better than glossy.
    Some more info:

  2. Shoulda seen my old setup. 5x 20 watt CFLs, a timer, a mains fan, all mounted in 2 plastic dustbins painted white (on the inside). Truly it was a beautiful sight! Did the job though, and cost next to nothing. It’s now long left behind, and I’ve given up gardening.

    What was handy, was hanging the bulbs from their wire. Clothes pegs on the top meant I could alter the height they hung at, meaning they were only ever a couple of inches from the growing plants. Not close enough to burn, but close enough to stop them stretching toward the light and growing stringy, which might happen in a situation like this, unless you’ve got more light than the Sun.

    Everything used 3-core earthed wire. In the UK we have a sensible earthing system with separate wires, usually connected to a water pipe, rather than the neutral line. Although light bulbs don’t have an earth connection, I figured earth as much as I could, since plants need water and all, just in case.

  3. Yeah, I use CFLs too. I enjoy “fresh greens year round”, especially CBD-rich “greens”.

    BTW, 6500K 18/6 veg then 11/13 2700K flower IMHO.

  4. jetcityorange and dont forget the thc rich greens too.

    since the setup takes 160 watts that is less than most grow lights so not such big electric bills thereby if you do decide to grow thc rich greens too the feds will not be able to use your electric bills as an indicator for suspicion.

  5. For anyone who doesn’t want to do all that wiring, go to your hardware store and look for the 3-5 light bathroom fixtures. They come cheap, prewired, and with a back plate that makes mounting easy.

    1. …and if you read the warning on the CFL’s you’ll find that you’re also not supposed to use them in enclosed fixtures for that very reason. This ‘hack’ needs a fan for cooling or the CFLs won’t last very long.

      Incidentally, Most if not all LED replacement lamps have the same restriction. It’s easier and probably cheaper, imo, to purchase a fixture and bulb that’s designed for this purpose than it is to make one.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.