DIY COB LED For General Gardening 3 Years Later

I didn’t realize it at the time, but the subject of COB (chip on board) LED lighting in a traditional gardening environment was surprisingly popular.  I wanted both better performance and save on the operational costs of preparing a garden indoors. 

Apparently I’m not the only one.


These are our primary DIY LED COB lighting rigs installed into our 4 foot by 4 foot tent. We get great coverage and each grow tray has its own COB, maximizing light distribution.

Making The Switch To DIY LED COB’s:


I switched to COB LED lighting for general indoor gardening purposes in 2017.  I’ve now used them for three growing seasons. I have two sets of the 4-COB kits that I built, so I have a good idea on their performance and capabilities.  I’ve used them in a tent environment and have now grown thousands of vegetables and flowers under them. I like them so much that I will likely invest into a third setup since we always have to break out our older CFL (compact flourescent) light every year.

It’s not a secret that COB LED’s are primarily geared towards cannabis growers. That’s not my purpose. For us, the decision to go COB was purely based on electrical cost. We pay almost 23 cents per kilowatt hour in the far north of Alaska, one of the most expensive rates in the nation.  COB LED systems are touted for some of the highest PAR (photosynthetically active radiation) output per watt of electricity.

DIY LED COB Performance & Operating Costs:


I used to quietly resent growing season a little bit. On average, my power bill would go up over $100 for a few months. This just isn’t the case with the COB’s. Even with three lights running 14 hours a day, the bump is closer to $50 per month. I can probably reduce that even further by swapping out the older CFL we still use.

Per light fixture, we are seeing roughly 125 watts of savings along with much better coverage and performance.  Across our two light systems that replaced our CFL’s, that’s almost 250 watts saved.  That adds up quickly when it comes to the power bill.

The COB’s are reliable performers compared to CFL counterparts. Despite operating 14 hours a day for many months out of the year, we haven’t had to replace any COB’s, LED drivers or other components. With CFL’s, we have had to replace 2 or 3 bulbs every year in each fixture, which usually cost about $10 each locally. That’s another $80 in operational costs we have saved compared to CFL’s over three years.

Ultimately, the COB LED’s reduced both electricity costs and general maintenance costs significantly.  We estimate these cost savings to be roughly $200 to $250 per growing year compared to our compact fluorescent grow lights we used previously.

Represented another way, for our garden, the operational cost of COB’s is about 13 cents per plant grown compared to 29 cents per plant with CFL’s.  That is an incredibly welcome change.


DIY COB’s Paid For Themselves:


What this means is that we’ve now almost paid for both lights in its entirety through cost savings alone.  At three years, we are at the point of enjoying pure cost savings due to the change to DIY COB LED’s.

We are seeing higher than usual savings due to our higher electrical costs.  If you were paying the national average electricity rate, or ~12 cents per kilowatt hour, the savings would be a little more difficult to justify.  Over time, though, you would still easily pay off the difference between CFL and DIY LED COB lighting systems.  If you are buying a new lighting system for your garden, COB’s make sense to consider.

The flexibility of our COB systems have allowed us to use our grow lights in different ways as well.  With the relatively low impact to our power bill, it has been much more enticing to use them more.  While this has resulted in some additional operational costs, we are also seeing additional benefits.

LED COB’s Grow Quality Plants:


Plant wise, we also couldn’t be happier. The COB’s provide a much better light distribution compared to the CFL’s. We get good, even coverage across our entire 4’x4′ tent with only minor dips at the extremities. This was a huge improvement over CFL’s and we often struggled with very low light levels at the sides of the tent. Eight LED COB’s in a 4’x4′ tent works quite well for us for general gardening purposes. The COB’s are also easier to deal with than the big and bulky T5 setups.

Another unexpected side benefit we’ve seen with the migration to COB’s is easier hardening off processes. We’ve found that the increased light levels allow the crops to harden off more quickly and successfully.  Our plants are used to higher intensity light when we put them outdoors. We can usually go from initial transplant from a seeding tray to the greenhouse within just a few days and the initial sun burn is almost non-existent.

How Do We Use Our DIY COB LED’s?


Functionally, our primary 4’x4′ COB grow tent serves four major purposes.

We start all seeds under it and the COB’s light levels have always given us short, compact plant starts in our 200 cell starter trays.  We get excellent germination rates as we can easily maintain 65 to 75 degree temperatures in our grow tent with just a single exhaust fan.

Another critical function we use the COB’s for is the first 2-3 days after transplanting our seedlings into larger pots. We see quick recovery, low stress levels and an explosion of growth within two days. We also maintain our warm climate (pepper and tomato) crops for almost the entire indoor season under the COB lights. The high intensity light is good at penetrating the plant canopy and allows for very high quality warm climate plant starts.

In the late season, we’ve found ourselves firing up the tent again to mature our peppers. It’s difficult for us up north to get “truly ripe” peppers, we just don’t get enough days of heat most years. I’m talking about red jalapenos and bright orange habs. We can usually take 9 or so pepper plants indoors and they finish out quite nicely in the tent within just a few days.

Lastly, we usually fire up one of the two COB lights in the tent again in the depths of winter.  Our house plants really struggle with the low light we receive in December and January.  We migrate most of our houseplants into our tent for 2-3 months over the winter, helping them survive the harsh winter up north.

I’ve done a little bit of full-cycle growth attempts under the COB’s as well. For the most part, the COB’s do great throughout the entire cycle for most of the plants I’ve tried. I played around with some Kratky method hydroponic lettuce and other plants.  While we haven’t gone into year-round production, it’s an option we’ve considered many times.

We see fair use out of the system and appreciate it’s flexibility to do everything we need.  Ultimately, we’re getting better performance compared to our CFL systems.

Do CFL Lights Still Have A Place?


We still use one of our two 2×4 6-bulb T5 CFL lights for plant overflow. We’ve found it beneficial to have a table dedicated to plants that we are hardening off so we can easily transition them inside and outside.

I am thinking one of this winter’s projects may be to build a third LED COB setup for this purpose. I might be interested in doing strip LED lighting as well, but the COB’s just seem easier and provide greater flexibility.



DIY LED COB’s Sysnopsis:


I’m extremely pleased that I made the switch to COB LED’s. We are at the point where we are enjoying pure cost savings from the reduction in electrical usage. Our garden starts are better than they ever have been. Hardening off processes are easier and more successful due to the higher light intensity. They just work year after year.

As for the future, what I’m watching are the studies on LED light spectrum. Companies like Fluence Engineering and others are definitely pursuing this, but I don’t think they are quite perfect yet. This next-gen LED technology is also very expensive at this time.  But, I think achieving a “perfect” light spectrum is very much a reality in coming years and I think LED technology can eventually make that relatively inexpensive.

I am hoping this science is fairly settled in a few years when I review my lighting systems again. I also am watching the efficacy per watt continually increase, so I’m hopeful the next-generation of LED’s will again be even more revolutionary. For now, though, I’m solidly in team COB for gardening purposes.

2 comments… add one
  • Khane Oct 19, 2020 @ 9:48

    I would really like to see how you build your lights. Do you have any plans available? I am new to the cob less but eager to learn. Your lights looks great!

    • Jeff Nov 20, 2020 @ 13:45

      Hi Khane! Thanks for the compliments, we like them a lot. I don’t really have any plans, but there are lots of ideas and details out there on YouTube and other places for designing and assembling these lights. Once you have a bill of materials, they aren’t difficult to assemble. I only had to use basic tools, such as a drill, wrenches and screwdrivers. I had never assembled one before, but I did spend some time making a good plan and from there, it wasn’t that hard.

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