Downside to LED grow lights:They're still rather expensive up front (compared to fluorescent tubes), at least the ones powerful enough to provide good amounts of light to plants. A 2W grow light bulb can illuminate a single African violet well enough, but you need considerably more for a plant table.
Other considerations in lighting choices:The shape and configuration of the light:
I want ones that I can use on a shelf-growing system, with lights mounted under a shelf, lighting the plants on the shelf below.
LED light colors:
LED grow lights are often sold with combinations of LED chips, usually red and blue. Other online sources can more adequately explain about photosynthetic active radiation (PAR), but generally, plants absorb light mostly in the red and blue peaks of the light spectrum. The illegal plant growers' sites elaborate more on this general idea: red light make plants bloom and stay compact, while the blue ones stimulate stem and leaf growth. However, my plants all get some sunlight through glass --some only quite indirectly --so they are not deprived of the whole solar spectrum. I am more or less just experimenting with the various colors.
My lights, thus far:1) Kessil H350 LED, Deep Purple. This one is supposed to be a bit heavier on the blue than red and comes out with a pinky-purple glow on the plants. This one lights a table of plants from about 24" above the plants and has a coverage of about 3 feet round. This is also the most expensive light, going for over $200 on Amazon, but you can occasionally find a deal on Amazon and get it for less. It makes a quiet whirring noise as it has internal fans.
|Kessil H350 Deep Purple LED light|
|Succulents illuminated by Kessil H350 Deep Purple|
2) Kessil H150 Blue. This color is supposed to be good for vegetative growth (i.e. not blooming and fruiting). I used it during the winter for growing herbs. Now, its helping the seedlings, though they probably get sunlight from the window anyhow. The LED light just makes the day longer. The light is suspended on light chain from an overhead cable stretching across the room. Kessils also have a separate transformer that dangles unattractively from my overhead cable.
|Blue light Kessil LED|
3) LED bulbs that fit in a regular E27 socket. I bought a 9W LED and a 45W bulb on eBay from China. The 9W bulb was purchased cheaply at $12 and the 45W one was $21. They provide mainly pinky-purple light, which may help the orchids bloom. These bulbs have cast aluminum housing and I assume the circumferential aluminum fins are meant to dissipate heat. The bulb never feels much warmer than room temperature, so the unit doesn't seem to heat up much. I understand that LED bulbs' lifespan depends on the ability to operate without a heat build-up; LED bulbs in confined spaces (small enclosed lamps/sconces/etc) have reduced lifespans. Mine should last a good length of time being unenclosed.
|45W LED bulb that hangs over the orchids|
|9W LED bulb on an E27 base, with 5 Red, 2 Blue LEDs|
3) Flat Panels of LEDs come in square or rectangle configurations and are shallow enough to use under shelves. I have covered the upper shelf here with clear vinyl (like the stuff used over tablecloths) to prevent water from dripping through into the lights. I used these to light seed-starting trays on the bottom shelf, where sunlight from the windows doesn't quite penetrate. My first 2 units are 14W units, one all white and one a mix of white and blue LED chips. I got these mostly because they were one sale online for $25 each. They had a small hole on each side and I made an ugly system with wire and S-hooks and carabiners to suspend them. I have a box of S-hooks, so I can easily add hooks to lower the lights if wanted. At 14W, they are not as bright as having four T8 tubes across the shelf.
|Square panel, 14W, with all white LEDs in aluminum housing|
|Square panel LED fixture suspended from metal shelf|
|Seedlings under white LED|
|Square panel 14W LED, blue and white mix of lights|
|Two interlocking 18W LED panels have red, blue and white lights|
4) Coming soon: UFO-style round LED units that can be suspended from above. I found a good deal (under $100 on Amazon) on a 135W Apollo GL45 UFO-style fixture with 3W LED chips, a feature which seems to be found in the better lights. I'm hoping this can fit under the shelves like the flat panels.