Common CFL and LED household bulbs (and IKEA 10W grow bulb) PPFD & footprint tested.
How well suitable are they for growing plants indoors?
Fellow growers. We see many of you on Reddit, Facebook, forums, and generally, on the internet try to grow all sorts of plants with a vast number of cool DIY light solutions. For the most part, unique and impressive solutions. We all have different needs for our grows and plants. Succulent have much different light requirements than basil or cannabis. Depending on what you want to grow you'll need a grow light that matches your plant's needs.
In this video, we test commonly used household bulbs (CFL & LED) with E27 socket. All lamps are warm white at 2700K. We test:
Bulbs : Distance
9.5W LED w dome : 6" / 15.2cm
9.5W LED no dome : 6" / 15.2cm
14W LED no dome : 6" / 15.2cm
9W CFL : 2" / 5.1 cm(!)
18W CFL : 6" / 15.2cm
We also do quick tests of 140W incandescent, 38W CFL vs 28.5W LED, and the Ikea 10W grow bulb (more in-depth tests in a coming article). The tests consist of testing PPFD values in umol/m2/s at specific spots underneath the light to map its light footprint.
How intense light (PPFD) is reaching the center spot underneath the lamp?
How does light spread over a 1x1' (30x30 cm) area?
Which lamp is better suited for growing plants, CFL or LED?
The list of tested bulbs was inspired by the common household lamps we’ve seen people use for indoor growing. Regular CFL or LED E27 or E26 socket bulbs can very well be used for growing plants, but under certain conditions. We know how much light certain plants require and we have now tested how much light certain lamps and bulbs emit. With this information, we can efficiently calculate if our plants are having their light requirements met.
A plant’s light requirement is presented in DLI (Daily Light Integral) which is determined by light intensity (PPFD) and photoperiod (hours of light). Low light intensity (PPFD) and short photoperiod (time) would result in a low DLI of between 0-5. On the other hand, a high DLI number would be in the 30s. A clear illustration of how light intensity (PPFD) and photoperiod are multiplied to calculate DLI:
LEDTonic's DLI chart and DLI (Daily Light Integral) explanation
Ok, but how do I do the math? How do I put this knowledge to practical use?
The example we use in the video is a typical window sill that has limited natural sunlight but the goal is to grow tomatoes.
We know that during summer the sun’s light reaches our plant with an intensity of 750 PPFD. We have full sun for 4-4.5 hours per day. After that no direct sunlight (very low PPFD).
Tomatoes require 22 DLI, as per our DLI chart and Dr. Lynette Morgan,
750 PPFD over 4-4.5 hours equal 10-12 DLI. This means we’re ~10 DLI short (22-12=10).
Assuming our tomato plant is 1x1’ (30x30 cm), using the 14W LED bulb at approx. 5.5” from the plant will result in 200 PPFD average over the plant’s canopy (1 sqft). This intensity over 14 hours results in 10 (10.1) DLI. 12 DLI from natural sunlight plus 10 DLI from our 14W LED bulb results in 22 DLI!
This means that supplementing limited sunlight with a 14W LED bulb and setting it up correctly can be enough to meet tomato plants’ light needs.
Plants with lower light requirements, such as basil (~12 DLI) can be grown exclusively under a 14W or maybe even a 9.5W LED with no additional sunlight.
The main result of the test
CFLs are rarely, if ever, a better choice than LEDs for growing plants. CFLs have other great features, but they are not suited for growing plants. CFLs spread their light, which from the get-go isn’t very intense, with no focus. A lot of light, even with reflectors, is not reaching its intended destination; a somewhat flat canopy. Even if the CFL would be angled and used as a vertical light, its light output and intensity is far lower than LEDs per watt consumed and it’s too low to do any meaningful impact on plants. Even plants with very low DLI requirements would struggle to have their needs met by CFLs at very close distance.
LEDs even without reflectors focus their light somewhat well to both create a decent light footprint and provide enough intensity for smaller plants.
With that said, regular household bulbs will never be as efficient and suited for growing plants as purposely designed LED grow lights or bulbs. The Ikea bulb is an example of this and we’ll also try to work our LEDTonic Z2 LED grow light into the test. The Z2 is a great indoor grow light for small and confined spaces. A household LED bulb may work well for a plant or two, but for larger operations, a proper grow light is recommended.
Still, if you’re a hobby grower and want to make do with what you have at home, you can still start an indoor garden with bulbs that you likely already have in your drawer.