No comparison, the T5s are far more efficient. Which T5 tube were you thinking of? Any difference in up front costs will rapidly be made back on electricity savings, three 54W T5s produce more light than one 200W VitaLume. Only choose the VitaLume if the straight tubes won't fit in your space.

When you are planning lighting above 200W or so, you should consider whether a metal halide of HPS system would be more convenient. If HPS is suitable then you should probably choose it since it is still the most efficient lighting source. A new metal halide running on digital gear has comparable efficiency to the T5s, you should compare it based on startup cost, convenience to your setup, and possibly bulb replacement costs (metal halides still can't quite match the lumen maintenance of the best fluorescents). A metal halide will almost certainly be a better solution than the VitaLume if your light source has to fit in a small space, more light and longer life. For example the 150W Philips Ceramic Metal Halide produces about the same light output as the 200W VitaLume, and higher powers are more efficient.

The metal halide has such an ugly lumen depreciation (65-80%) and a lower range in lamp life than the other HID lamp types and fluorescents that I asked my prof why anyone would use one. I think they're an abysmal light source and it irks me that new systems are still sold, normally citing initial lumens and conveniently failing to mention how significantly that degrades.

Lumen depreciation on high pressure sodium is a very respectable 10%.

As shrubs_n_bulbs indicated, the CFLs aren't very efficient. The T5HOs are a better choice from that standpoint. You might also look at the following comparative article of T5, T5HO and T8. http://ecmweb.com/ops/electric_fluorescent_lamp_coming/

Here is a link that might be useful: Comparison of HID to T5HO

Another biased article that makes the same old mistake of comparing old technology HID lighting with the best available fluorescent technology. It also makes the common mistake of assuming that T5s are somehow an efficiency advance over T8s, whereas the best of each are more or less indistinguishable.

It does at least throw in the last paragraph with a hint that metal halide technology may eventually catch up. Well, that day is here, electronic (digital) ballasts for metal halides are here and you'd be a fool to use anything else, pulse start has been around for years, and ceramic metal halides are here if you need good colour rendering (not that you really do for plants). The best metal halides today operate essentially to the same specs as the best fluorescent technology, which is a good bit better than the fluorescents that 90% of people are using.

Another mistake is comparing low power HID lamps with fluorescents. HID lamps only achieve their best efficiencies at higher powers, ideally 400W or more. Metal halides still offer the highest efficiencies available, fluorescents offer more spectrum options (although not all are available in T5 format), and metal halide lumen maintenance is still slightly worse. Which you would choose will depend largely on how much total power you need, since a metal halide less than 400W is less efficient than available fluorescents and above 400W you start to need a great many fluorescent tubes just to achieve lower lighting levels. Possibly you may be influenced by the need for a particular spectrum or the even spread of light from a whole array of fluorescent tubes instead of a single intense metal halide source. Factors like dimming and slow switching (restrike on metal halides is much improved but still horrible) are probably not relevant for growing plants. And probably fluorescent lighting's biggest drawback, that it doesn't work well in cold conditions, is also not likely to be relevant.

Likewise the decision between T5 and T8 is not that one is better than the other. The only advantage that the best T5s have over the best T8s is that they can produce more light in the same space because the tubes are thinner and they are effectively overdriven straight off the shelf. If T8 tubes can produce sufficient light for your needs in the available space, then you should pick T8s because they are cheaper and easily available in more spectrums. If you need more light from the available space then you should choose T5, probably T5HO, or you could overdrive T8s (US T8s are actually underdriven and efficiencies can even improve slightly with overdiving).

shrubs_n_bulbs,

If the metal halides have caught up due to electronic ballasts, could you please describe what the current lumen depreciation is on the MH lamps? On all the systems I investigated, that piece was conspiciously absent, so I've been operating on what I have learned in the past.

Also, based on the second article I referenced (http://ecmweb.com/ops/electric_fluorescent_lamp_coming/ ) I really don't like the T5HOs at all compared to T5 and T8s. Here's an excerpt consisting of the table that sums up why:

Also, is your statement that US T8s are underdriven the reason why my two-lamp 40 watt luminaire is apparently drawing 53 watts? The input watts for the ballasts I've been looking at from American Fluorescent range from 52.2 to 86.5 watts. The best lamp/luminaire combination they have appears to be a 59.3 watt electronic ballast with 2 F32T8s delivering 5415 lumens.

Ok you guys have completely confused me.
If I understand correctly , you are saying that 8 HO T5 is better for growing plants then MH ?
8 HO T5 X 54 watts = 432 watts total so we can compare this setup with 1 MH 430 watts.
Are you only looking at number or have actually have hands on experience?
My guess is that 1 430 watts MH is much better at growing plants then 8 HO T5.
The main reason is penetration for MH is much higher then for the T5 even is both system is using approx the same number of watts. Correct ?
Better penetration = better crops. This is very important unless you are only growing plants under 24".
1 430 watts MH is 50-70$
8 Ho T5 54 watts is 17$ X 8 = 136$
Let's say the MH needs to be replace 3 times more often then the T5, the cost would be similar but you would get better results with the MH.
So my little brain is telling me that the MH solution is better then the T5 in dollars and efficiency (growing plants).

Thanks for the reply, "Vitlme is suited to a more intense focus of light (lighting a smaller area) than the '"(T5)"', which will give you a wider dispersion of usable light." is another reply I recieved. I would say that in my experience the 400W MH was a great bulb for me. It is what got my plants by when I had no suitable light and it made a great area to try some new stuff such as an Aristolochia! I did begin with the incandescent bulbs and fluro tubes and was happy there too but the light was not as intense, using the two T12's. Right now I am getting by again with 4 daylight T8's and mylar, over and under my plants with a small mattress heating pad for some warmth. The plants are doing splendidly with the lights no further than 6" and are even setting bloom with red's and purple's coming out bright and very dark in their stems and leaves. My plants have even adjusted to growing directly into the reflectors behind the tubes, although some yellowing did occur at first from saturation. I would say I am happy with the flurescents now because of low cost and all around maintinence. I can spray the plants with water without worry of shattering a bulb and it seems to me that fluor's can be compared to the point and shoot camera of ease for indoor growing. Most of the light work has been taken care of as long as the distance is close up and you have a reflective environment. No heat issues, good even spectrum spread, and a steady concionce knowing there are fewer safety risks involved. I would think the MH is a good strong light and is best used in a larger, more controlled growing environment. Where hazards can be less negligable and high light at large distances is required. Such as in a greenhouse. I did notice that the growth under my 400W MH did suffer at times due to the distance and heat issues, especially with Gardenia's and other fragiles. So fluro's can be a real 'life' saver where close light proximity applies! Mind you this is only a subjective issue as all the environments were in a house, either bedroom or basement. So the air was not always the best. I really don't think that I would grow plants too far from the light source. No more than 18" perhaps under a 400 watt unit. Otherwise there will be quality issues with growth at a certain distance. This is why I think that greenhouses use the MH/HPS as supplemental light.
Everything I have just said is only pertinant to my experience though and should not be given too much consideration as the variables are great. My friend has a MH too and I know that her plants suffer under it in the winter because of its proximity issues to the plants themselves, Aphids, lanky, weakened discolored growth mainly. She saw the growth under the 4 32W T8 mylar and was blown away by the colors, vigor and fantastic contained environment, humidity, heat, etc. As I said, easy, cheap, all-in-one. I would recomend it as being a more subdued and intimate experience growing under fluorescents rather than the MH/HPS in your house. Up close and personal, your plants will love the experience! For me the key has been to contain the warmth, humidity, and light in a small environment.
I won't argue with any of you about it though! I feel everyone is entitled to their own opinion.

Please pardon my spelling errors! I do not check sometimes as I usually write to ease my insomnia at odd hours! I am sorry for the poor use of the language! Just note, I am passionate about plants and I was hoping to share some of that with someone, as I know you all do! If not in a more "pristine" and well versed fashion. :)
- At a moments notice we are all leading a new life to the timid minds eye. - my Anxt

could you please describe what the current lumen depreciation is on the MH lamps?

It varies depending on the lamp, the ballast, and the starting mechanism. At best, just under 90%, more usually 80%-85%. Standard T5 and T8 triphosphor tubes give 85%-90%, and top quality triphosphors give around 95%. Take the numbers in your chart with a pinch of salt, specs vary. For example, the 16,000 hour life for the T5s is weird since almost every T5 manufacturer quotes at least 20,000 hours. Also, the 97% lumen maintenance is something I've never seen on a manufacturer spec sheet, perhaps this is lumen maintenance to 40% of lifetime?

I really don't like the T5HOs at all compared to T5 and T8s

I assume your main reason is the "system efficacy" numbers? Well that all depends on your "system"! Anyway, as I mentioned before on this thread or one of the others, T8s are certainly the equal of T5s in every respect except size, and they are cheaper.

is your statement that US T8s are underdriven the reason why my two-lamp 40 watt luminaire is apparently drawing 53 watts

No, probably you have a crap ballast! I have no idea what ballast is inside your "40W" luminaire, but a typical system in the US driving T8 tubes is nominally running each tube at 32W. Very often the ballast design is such that the tubes are actually being run closer to 28W. This is done intentionally to provide the same lumen output that a 40W T12 did, say 20 years ago, but using much less electricity. This is not very helpful to us plant growers! Examine the specs for any ballast you wish to use, in particular the ballast factor. Numbers like 0.8 indicate efficiency but low light output, aim for something close to 1.0. Ballasts are even available with ballast factors above 1.0, indicating that the tubes are being slightly overdriven compared to that 32W nominal level, these are useful for growing plants since they give increased light with no loss of efficiency. European spec ballast operate T8s at a nominal 36W and they can easily be run up to about 40W with no loss of efficiency or life if you can find a suitable ballast.

If I understand correctly , you are saying that 8 HO T5 is better for growing plants then MH ?
I certainly didn't say that. 8 54W T5 tubes are very similar in total light output, total energy use, lifetime, cost, and lumen maintenance to a single 400W metal halide bulb, assuming both are new designs and driven on modern electronic gear.

My guess is that 1 430 watts MH is much better at growing plants then 8 HO T5.
The main reason is penetration for MH is much higher then for the T5 even is both system is using approx the same number of watts. Correct ?
You've been reading too many pot grower forums :) Those guys are so stoned they don't even know what penetration is, it just sounds good and there is this theory that metal halide is king because it has better penetration. Penetration is a measure of how slowly the light decreases with distance, and this is usually best for a high power light source mounted a long way from the plants (the sun is pretty good, try it some time!) and that describes a 400W HID pretty well. But a 400W total fluorescent system is just as good, provided with proper reflectors or baffles. So no, not correct. Also, don't read too much into what the aquarium guys say about penetration, they are dealing with very different issues trying to get light through water to the bottom of a tank.

Let's say the MH needs to be replace 3 times more often then the T5,
A decent metal halide run on modern switchgear can be run to failure, or say 20,000 hours of you don't like the idea of an exploding metal halide bulb. A T5 should also be run to failure, so I would compare them both on the same replacement schedule. Growers with crap old equipment may still need to replace their bulbs or tubes every 6 months but they really need to move into the 21st century.

the cost would be similar but you would get better results with the MH.
So my little brain is telling me that the MH solution is better then the T5 in dollars and efficiency (growing plants).
Sounds to me like you already made up your mind which is best and you're trying to justify it? T5 bulbs are expensive, maybe you can buy a 400W metal halide bulb for the price of 8 T5s, maybe even for about the same cost as 3 T5s (replacing 3 times as often), but probably not a very good one. If cost is your main driver then use T8 tubes, just as efficient, need a lot of tubes but they only cost $2 each :) Metal halides are convenient and efficient in high power situations but there are not huge cost benefits over fluorescents, by all means use them if you don't mind running 100' of wire betwen all your ballasts and tubes!

the light was not as intense, using the two T12's
Well duuuhhh!!! Always compare like with like. 2x40W fluorescents is never going to be comparable to a 400W HID. If you compare to an 80W HID you may well find the fluorescents to be better since low power HID bulbs are not very efficient. Besides, the majority of T12 setups are far from modern technology, very inefficient and so not good light output. Even trying to compare maximum light intensity close to the bulb is not very relevant, sure the metal halide has a higher intensity two inches from the bulb but you can't grow plants two inches from it so what does it matter?

4 daylight T8's and mylar
I use 4x36W T8s for an eight square foot growing area in winter, in my opinion it is the best solution for moderate growing spaces. I would use HID if I needed to light a much larger area and I use compact fluorescents in my small propagator.

-- could you please describe what the current lumen depreciation is on the MH lamps?
- It varies depending on the lamp, the ballast, and the starting mechanism. At best, just under 90%, more usually 80%-85%.

Do you have a reference that I can provide to my lighting professor? I've already felt compelled update him on his (albiet brief) LED lecture section--he told us that LED efficacy was ~200 lpw (ACK!). I believe that has been accomplished in lab, but it's hardly what is commercially available today. Since we're studying architectural engineering, we need the applied stuff!

-For example, the 16,000 hour life for the T5s is weird since almost every T5 manufacturer quotes at least 20,000 hours. Also, the 97% lumen maintenance is something I've never seen on a manufacturer spec sheet, perhaps this is lumen maintenance to 40% of lifetime?

The T5 (improved triphosphor) line on the chart I have for fluorescent lumen depreciation essentially flatlines at 95% after 15K hours, so I'm not sure which is correct. 95% or 97% is splitting hairs, but it looks like they're pretty consistently 5% better on efficacy than T8. For 5%, I'll stick with my stockpile of T8s.

-- I really don't like the T5HOs at all compared to T5 and T8s
- I assume your main reason is the "system efficacy" numbers

That, plus the cost of the T5HO systems and that the T5HO systems' strengths is the (1) design flexibility afforded by being able to produce more light with fewer/smaller fixtures and (2) alternative to HID for high bay lighting. Both the strong suits of T5HO are geared towards lighting for humans, not for plants. Plants are (1) not concerned about pleasing architectural design and (2) as far as high-bay lighting goes, it's intrinsically a no-no for providing light energy to plants, since that distance^2 factor in the denominator is going to get you!

-- is your statement that US T8s are underdriven the reason why my two-lamp 40 watt luminaire is apparently drawing 53 watts
- No, probably you have a crap ballast! ...US driving T8 tubes ... done intentionally to provide the same lumen output that a 40W T12 did, say 20 years ago ... This is not very helpful to us plant growers!

Yes, the US does some smart things, and a whole lot of dumb things. The root seems to be something along the lines of "we've always done it this way." I've lived in W. Germany (9 years) and Japan (6 years) and am very impressed how relatively more flexible the people are in those locations about embracing change. Sometimes it amazes me that my country manages to still thrive, perhaps partly on momentum, perhaps partly on the two big oceans on our east and west borders and the limited threats on these continents. Americans don't seem to believe that we should be required to actually think about the way we do things or consider changing the way we do anything...

But back to lighting, is the "weaker" standard US ballast a real negative apart from the space ineffeciency? I already have a dozen luminaires, purchased in the days before I knew anything about lighting. I use mylar to reflect light and keep the lamps practically touching the plants. If one already owns the equipment, what are the pros and cons of acquiring a luminaire with a higher ballast factor? I know that they're around--I've seen as high as 1.1 on spec sheets for some of the zonal cavity calc's we've had to do.

Do you have a reference that I can provide to my lighting professor?
Venture lighting quote a 90% lumen maintenance for their Natural White" ceramic metal halides on pulse start electronic ballasts. I haven't been able to find an actual light output graph (not that's large enough to read anyway!) and I suspect they are quoting 90% at 40% of life, actual lumen maintenance to end of life would then be closer to 85%.

I believe that has been accomplished in lab
I don't. Certainly not a white light LED. Nichia has a 150 lm/W white light LED and are hoping for 200 lm/W in 1-2 years. There may be a 200 lm/W green LED in a lab somewhere, but there isn't and never will be a 200lm/W red (630nm or longer) light of any kind, it isn't possible.

The T5 (improved triphosphor) line on the chart I have for fluorescent lumen depreciation essentially flatlines at 95% after 15K hours, so I'm not sure which is correct. 95% or 97% is splitting hairs, but it looks like they're pretty consistently 5% better on efficacy than T8. For 5%, I'll stick with my stockpile of T8s.
Good quality triphosphor T8s are exactly the same, flatlining at 95% for the last half of their lives. Don't be fooled by the fact that inferior technology is available in T8s but not so much in T5 format. Look up the specs for something like the GE Polylux XL or Osram Lumilux. That 5% difference is equivalent to two or three dollars electricity over the life of a tube so probably not worth discarding a 90% tube for that alone, but the better spec tubes usually also have slightly more initial lumens and longer lives.

is the "weaker" standard US ballast a real negative apart from the space ineffeciency
It is really just a space inefficiency, an inability to produce more than a certain amount of light from a certain space. So long as you can produce enough light in the available space, look for maximum efficiency and US spec T8s operate at about their maximum efficiency. Once you can't get enough light any more, look to standard T5s, overdriven T8s, high output tubes in any format ("high output" is exactly the same thing as overdriving, it just comes with a warranty!), compact fluorescents, or HID lighting.