"I've also been thinking that there are CFLs and LEDs at the 6500k range that are obviously much less expensive. "

You must mean that the price per bulb is less expensive which is a nonsensical basis for comparison. Almost but not quite ideally, you want to compare the cost of lighting by various methods on the basis equal power output within the photosynthetically active region (PAR) of the light spectrum, 400 - 700 nm. Since that information is rarely given in bulb specifications, the next best thing is to compare cost per bulb and the cost of electricity per lumen output which incorporates human eye sensitivity. Color temperature is relatively unimportant. That Amazon ad does not give lumen rating of the Plusrite bulbs; shame on them. But, elsewhere I found the initial rating to be 5000 lumens per bulb. With these bulbs, your fixture puts out approximately 40000 lumens at about 450 watts. if you include the power consumption of ballasts. To match that with $2.50 Philips 800 lumen, 8.5 watt LED bulbs, you would need 40000/800 = 50 bulbs at a total cost of $125, more, if you include the cost of fixtures for the bulbs. The power consumption of these LED bulbs would be 50*8.5 = 425 watts, slightly better than your T5 fluorescent. And, I can tell you that, at equal lumens, there would be more power output within the PAR with LED.

"Even having eight CFLs at 100W (effective) output each would be less expensive than powering the one florescent fixture."

No, not eight. A typical 23 watt "100W equivalent" CFL produces 1600 lumens therefore you need 40000/1600 = 25 bulbs to match the lumen output of your T5 fixture and those CFL bulbs would consume 25*23 = 575 watts.

Very interesting. Thanks so much for the info.

"You must mean that the price per bulb is less expensive which is a nonsensical basis for comparison."
Yes, I was assuming an otherwise equivalence in terms of lumens, but that doesn't seem to be the case.

Are you saying it's not necessary to use the 6500k for growing basil, cilantro and dill? Any chance I could use the T5 LED bulbs at 5000k?
http://www.amazon.com/Hyperikon%C2%AE-equivalent-100-277V-Dual-End-UL-Pending/dp/B00YWG5L0C

Thanks,

Dave

You also can't assume any of these published numbers represent actual power consumption, for a variety of reasons. You really should use a kill-a-watt or similar meter (thankfully not an expensive purchase) to monitor how much power is consumed by each fixture. The numbers you get may be significantly different than you expect.

I actually already have one of those. I remember running it on the fixture a year or so ago to try to calculate operating costs, but don't even remember now what it showed.