Note: if your lazy and dont want to read alot of boring and nerdy stuff skip to the summary towards the end, its in red.
Sorry Loki but LEDs are nowhere near being a replacement for HPS/MH.
LEDs dont give off nearly enough light to efficiently grow light demanding plants. Do not forget that LEDs also only produce usable light in a very narrow angle... What I mean is that most "high power" (10k+ MCD) LEDs have at best a 15 degree angle of actual light. There are LEDs with a much wider light angle, however they are very poor at producing usable light.
anticipated response:
"10K+ MCD is shit" (the average MCD of your typical LED is about 2-5k)
Your right. The other alternative would be to use the (usually) star shaped LEDs that give off (last time I checked) up to 5W of power, however the whole lighting angle from above still applies. Another problem with these is that they create an insane amount of heat! Heat will lower an LEDs light output and shorten its life span.
anticipated response:
"thats bs LEDs dont get hot to the touch"
OHRLY? Then explain why they use massive (2-3x bigger then the led) heatsinks to keep them from cooking themselves?
Another point about LEDs. White/Blue (5000-6000K) leds produce very low output. Red/Yellow leds by far produce the most light. If you could cool them properly (and lets face it a bunch of 5W leds in an enclosed housing with a bunch of heat sinks isnt going to be adequate cooling) then sure its possible that you could have a viable flowering light.
anticipated response:
"okay so whats the problem? you just proved me right!"
Sort of. The amount of leds you would require to produce enough light would be in the hundreds, and thats for one plant only!
Dont even get me started on the whole issue of powering the leds. You cant simply plug them into the wall and expect them to work. You would need a AC-DC power supply, which in turn makes more heat, uses more power and raises cost even further.
Correct me if I'm wrong but isnt the whole purpose of leds to reduce overall cost? Having to buy a shitload of wire, fabricate some sort of custom housing, a power supply that can deliver the proper voltage and amperage, and hundreds (if not thousands) of leds is not what I'd call cheap.
Last time I checked a 3W led sold for a whopping 25 dollars! Say you need 100 of them (300W), thats already $250, plus say $25 for wire, $50 for some ghetto ass housing, $50 for some pos no name pc psu and lets say another $50 for a good soldering iron/solder/flux/etc. your already looking at $425. I haven't even touched on shipping & handling (or cooling for that matter)
For that much money I'd rather buy a 600W+ HPS. If your looking for a small amount of plants then go CFL.
WARNING! (oh shi run for the hills)
It's been a while since ive done anything serious with leds so theres a possibilty some of my numbers are off however everything stated above still applies.
Anyways, thats just my 2 cents.
Summary for the lazy:
Yes, it is possible to grow plants using LEDS. Is it a viable solution? Not really. CFL would be cheaper and more effective for small grows and not even a possibilty for a bigger number of plants.
WARNING! (oh shi keep running mang)
I might be new to the forums but I know my way around electricity.