guess it depends on your budget.. the T5 will be the cheapest option, followed by HID (HPS/MH) and then LED.. the HID option also puts out a lot of heat so cooling will be required in an enclosed area.

for electricity, both T5 and HID are comparable. T5 slightly more efficient at lumens per watt.. at least using the 54W T5 tubes, a 4 bulb T5 54W fixture = 215W~ and puts out about 20,000 lumens (92 lumens per watt). a 250W MH lamp puts out about 21,000 lumens (84 lumens per watt).

personally, for something like basil i would go with T5 florescent.. if you were growing fruiting plants like tomato, peppers, etc. i'd go with HID because light can penetrate better at higher distance, the T5 would have to be kept about 1 foot above the plants at most, where as the HID bulbs 2-3 ft. i would guess a 4 bulb, 4ft T5 fixture would cover about a 4-5ft x 3ft area. most efficient T5 fixtures are the ones with highly polished reflectors to maximize light output. worth the extra money compared to the cheaper T5 fixture where half the light goes to waste (the top half of the bulb). i recently purchased a 4 bulb T5 fixture at homedepot for $90. the bulbs i purchased at a hydro store for about $7/ea.

For "top level" supplemental greenhouse lighting, you should want a fixture that does not cast a large shadow thereby blocking daylight. That precludes most T5 fixtures. The efficiency of HID bulbs increases greatly with wattage. The lumen efficiency of a 1000 watt High Pressure Sodium (HPS) bulb is 130-155 lumens per watt. You cannot beat that efficiency with any fluorescent light. HPS is preferable to Metal Halide because you are getting enough blue from daylight and HPS has practically no blue.

Thanks aruzinsky but what about cloudy days? Will the HPS still be effective without the blue? (I am assuming the blue is necessary for vegetative growth!)

@ aruzinsky

only HPS has better efficiency, yes.. but i'm referring to MH for vegetative growth which put out less lumens/light and much closer to the output of a good T5 setup with polished reflectors using similar wattage while also generating much less heat. also, a 4ft T5 fixture only weights like 10-15lbs.. my 250W HID fixture which is designed for plants weighs like 60lbs due to the integrated ballasts. it's also easier to swap out spectrum color bulbs for T5 fixture. there have been tons of improvements in florescent grow bulbs over the last couple years.

http://htgsupply.com/Category-T5-Fluorescent

I have the "Pure Par" bulbs which are designed for optimum vegetative growth: [http://htgsupply.com/Product-AgroMax-4ft-T5-Pure-Par-Bulbs

my leafy green plants love it and i get some explosive growth..

Stevie,

1000 W MH bulbs are up to 120 lumen/watt. If you look here,

http://www.ebay.com/bhp/1000-watt-grow-light

you can find HID fixtures with remote ballasts that will operate either MH or HPS bulbs, i.e., the hanging part is not heavy and switching between HPS and MH bulbs is easy.

But, thank you for the information about AgroMax fluorescent. They seem to have good spectral power distributions and are half the price of similar fluorescent bulbs. If I weren't so preoccupied with LEDs, I would buy some. I also see interesting claims made about UV bulbs.

Lisa,

I have no experience growing basil. Since you already have T5 fixtures, why don't you run a small scale experiment using mostly red versus mostly blue T5 bulbs on basil?

From Stevie's links,

mostly blue: http://htgsupply.com/Product-AgroMax-4ft-T5-Pure-Par-Bulbs

mostly red: http://htgsupply.com/Product-AgroMax-4ft-T5-Pure-Bloom-Bulbs

Based on the results of that experiment, you can decide between MH and HPS for a larger scale operation.