Pretty much everything in the longer posts by simpletbrain above is garbage. Don't use 5000k bulbs when 6500k are available. He's using mini LEDs instead of 1w LEDs. His math is totally and completely wrong on the LEDs and with respect to light/distance for HPS and MH (lumen output for HID lighting is determined much farther away than for CFLs). HPS and MH put out gobs of light at the 400mh and 700mh spectrum...for God's sake, pretty much everyone has grown and grown well with MH and HPS. Check the grow logs on here. Light from any source decreases in intensity in exponential relation to distance; the amount is the square of the distance form the source. Double any distance from a source and the amount of light will be one quarter of the previous amount. This goes for M,. Hps, CFL...everything. It's why you have to keep CFLs very close to plants...within 1? or (at most) 2?. At 3? from the plant, the plant gets ¼ the amount of light it gets if the CFL is only 1 1/2? away. Small distance changes from plants are much more important in CFLs grows...a shift of 2? (from, say, 10? to 12?) with MH and HPS will have some effect, but not a huge one. A change from 2? to 4? with CFLs is the difference between growing something and getting pretty much nothing. I'd pretty much ignore those particular posts, unless you want to tell everyone who is growing/has grown with HPS and MH that their lights don't work.

CFLs do work very well for two types of grows: SOG/SCROG and microgrows (less than 2 sq. ft.). The story that CFLs do not generate heat is false; they generate plenty of heat. You just don't feel it unless you've got a lot of them in a small space. Unfortunately if you grow two or more plants, you're going to need a buttload of CFLs in a small space. A 12? x 24? area will require about 150s of CFLs??6 of the 23-26w bulbs. You won't get much canopy penetration either (the distance square law applies to CFLS too), so you'll often need/want supplementary light. That's why CFLs are great for vegging...the plants aren't too big yet. Canopy penetration isn't as necessary. CFLs still work for flowering, but they don't work as well for the reasons noted above.

For what you're talking about...I?d go with a 150w or 250w HPS. You should be able to pick either one up for between $80-130. A 150 should work for two plants, and it won't generate too much heat. To match up with the 15,000 lumens you'll get from a 150w Hps, you'd need about 9-10 23w CFLs; 6-8 on top, and 2-3 for side coverage to help with under canopy growth. Even if you use two clamp lights and Y-connectors with four bulbs each, you'll be shelling out $7-80 for that. It's right on the border of whether it's worth it. If you really want to keep your grow small (as in: under 2 or 2,.5 sq. ft.), CFLs are better. After that, go for a small HID light.
Roughrider Reviewed by Roughrider on . HPS vs CFL Light Question NEED ADVICE!!! I am currently growing two plants with 6 23w CFLs. Both plants are about 6 weeks old, and they are looking amazing. I know that the flowering stage is coming up pretty soon, and im kinda low on cash. I know that HPS can get pretty pricey. So my question is, would it be a bad decision to flower the plants with the CFLs? What kind of yeild can i except with the 6 CFLs vs HPS. Also if i really should get HPS what wattage do you guys recomend for a 3.5ft x 3.5ft x 3.5ft plastic grow box lined with Rating: 5