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#1
10/18/2007, 10:28 AM
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MH and t5 power consumption
It seems to be generally accepted that T5's have moderately to significantly lower running costs (kw/h) than equal watts of MH. If true, why this is the case?
My understanding is that wattage, which is a unit of energy, refers to the amount the bulb (or ballast) is using to run. (Hence, wattage per gallon isn't a good measure for the appropriate amount of lighting for a tank). If this is the case, then why do, for example, ~ 300 watts of T5's (6 54w bulbs) cost less to run than 300 watts of metal halide (two 150's)? Yes, I know there are lots of variables, particularly with type of ballast, etc. For this exercise, please assume an optimally efficient 324w T5 setup as comparted to an optimally efficient 300w MH setup. My research indicates that MH bulbs generally burn a few more watts than they are listed at (ex: 400 watt MH bulb might burn 420, etc), but that wouldn't seem to make up the allegedly large difference in running costs. Can ballasts alone make up the difference in running costs, or is it smaller than people think? Please don't hijack this thread into a battle of which type is objectively/subjectively better--I would like to keep in on power consumption. Thanks for your input!
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Mike D |
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#3
10/24/2007, 07:04 PM
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use a kill-0-watt meter to determine actual consumption...but barring the overdriving ballasts, energy loss from resistance etc, 300 watts is 300 watts, and you will get charged by your utility for 300 watts.
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#4
10/24/2007, 07:48 PM
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MH bulbs kick off a lot of heat compared to t5. That heat then ahs to be delt with by a chiller. And all that heat has to be delt with by the AC in your house. So its not just the light that has to be factored into operating costs, but coolings costs as well.
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#5
10/24/2007, 08:09 PM
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Quote:
One would normally suppliment the 300w of halide with a couple actinic t5's or pc's. Put's you up to at least 378w (2 39w t5's) or more with pc's. So for 300w of t5's you can accomplish the same as the 379+w combo. |
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#7
10/24/2007, 08:21 PM
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T5s kick off alot of heat compared to Halides actually...
 Just because T5s have 40x the surface area per watt to shed their heat, doesnt mean that their net heat output is less. T5s and halides are about the same actually. But there is something to T5s that can allow them to grow corals with less intensity... most likely something in their spectrum, so sometimes, depending on the corals you keep, you can get away with less in T5 wattage than you did with halides... but not always. Otherwise, yes, a watt is a watt, and 1000 watts per hour (kwh) is always going to be the same for residential consumers of electricity. Something that they dont always tell you is what the actual wattage of various ballasts are at the socket. Many 54wattT5s are really running about 60 watts each. Many 250wattDE haldies on Icecaps are really 275-280 watts, and 250wattDE bulbs on HQI/M80 can run 320 watts or more easily (rarely under 300). These are the actual numbers used to calculate lumen/watt efficiencies. The one advantage T5s have over halides is as you go bluer T5s can maintain their output better than halides. Going from a 3000-5000K halide to 10,000K often cuts the output in half, and then again to go to 20,000K usually (depends on the wattage, 400s maintain better). T5s often only lose about 30% when going from 3000K to 460nm blue (20,000K). Still, halides can start out at 105 lumens/watt at 3000K, and T5s start at about 85-90 lumens per watt for a 3000K. So somewhere around the '10,000-12,000K' mark, they overlap in output. So its really a matter of spectrum. If you like the 'deep blue sea' 20,000K look, the I suggest T5s all the way. IF you prefer 'daylight', then halides. If you prefer a bit of both... then a combo of both.
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"If at first, the idea is not absurd, then there is no hope for it" -Al Einstein |
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#8
10/25/2007, 07:08 AM
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Since everyone agrees watts are watts, T5's should only be considered more "efficient" as far as your power bill goes if you have to run less watts to get the same results as MH, right? Wouldn't this mean that T5's put out more PAR per watt than MH?
In turn, if this is the case, why do I read over and over on this forum people recommending the same number of watts of T5's (or more!) to replace MH's? (Let's assume no chiller in the equation)
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Mike D |
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#10
10/25/2007, 08:26 AM
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crossi92:
That makes sense to me (assuming the T5's are more efficient). I did read an article or FAQ somewhere which claimed that 254 watts of T5 was "equivalent" (whatever that means) to 400 watts of MH. If true, one could get away with fewer watts burned for the same results. BTW, how has your lighting worked out? No complaints I assume? After seeing so many of the magnificent T5 only tanks here I am convinced they are as good as advertised. I just want to know how I can keep my power bill as low as possible!
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Mike D |
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#12
10/25/2007, 11:33 AM
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I provided the info in my last post. Halides are more efficient than T5s (at 3000K at least). It really depends on the spectrum of bulbs being compared though. A 10,000K halide will simply blow a T5 out of the water. Otherwise, yes, the advantage would be that with certain situations, you can get away with less T5s than you would halides.
That depends on the tank volume, its height, its inhabitants, etc. For instance, if your intention is a 500g acro habitat with alot of light-whoring species of coral and clams... halides might be better. FWIW, I have found the most efficient lighting combo to be just 10,000Kish halides combined with blue+ style T5s. Halides are better at making daylight, T5s are better at making blue (since their base color if the tube was clear is neon/argon-UV/purple vs. the base color of a halide which is determined by the gasses in the jacket). In theory, T5s should be more efficient, but when it comes to making daylight, the conversion that the phosphors have to do to get daylight isnt as good as the raw ability of a halide to ignite halide gasses into a plasma like state. But blue light (higher frequency) is harder to make than red light because the shorter the nm of the light, the higher the power needed to create it. Thats why, in theory, since T5s are making blue light better than halides, they should be the stronger bulb with making daylight as well... but it just isnt so.
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"If at first, the idea is not absurd, then there is no hope for it" -Al Einstein |
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#13
10/25/2007, 02:53 PM
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hahnmeister:
I understood you last post to mean that they were more efficient (at certain wavelengths) considering lumens per watt, not PAR per watt (which is what I thought mattered). I have found various PAR ratings, but so much depends on the ballast and reflector (of which there are soooo many combos) that it is hard to get a general sense. But perhaps higher PAR tracks higher lumens. I don't know. Speaking of which (not to hijack my own thread), along with my tank upgrade to a 120 I need to upgrade my lights. I was planning on the 2 x 150w HQI, 2 x 54w T5 retro kit from Hellolights. My idea is that I will have a couple bright areas from the 150's, overall good coverage from the T5's, and the ability to add a few more T5's later as I wish/need. (My tank, btw, is 60"L x 24"H x 18"D). I was leaning towards either 10k MH's with actinic T5's, or the 14k MH's with Blue + T5's. Any suggestions?
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Mike D |
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#14
10/25/2007, 05:39 PM
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Most lighting companies dont give PAR figures... so we have to rely on lumens. True, as a light gets bluer, it will have an even lower lumen in proportion to PAR, but this is pretty true of T5s and halides both. None the less, there is a small difference since T5s can be '20,000K blue' with little to no daylight... even the bluest 20,000K halide still throws some daylight. But considering the lumen output of a 20,000K halide is usually in the 20 lpw range... arguing even a 10-15% innacuracy due to the lumen 'scale' isnt going to mean much when a blue+ T5 can be almost double the lpw with a 'blue+' style bulb. But is anyone out there going to run their tank with 100% blue+ bulbs? That has its own disadvantages with photoinhibition anyways. So you often run at most 2:1 blue to daylight bulbs... and daylight T5s dont exactly jump up as you go 'warmer' like halides. So for our uses, where we often want 1/2 blue light, 1/2 daylight in our tanks... halide vs. T5 is a real crapshoot. If you lean towards the more 20,000K range, then T5s might be a better choice... but like I said... that comes with its own problems (blue light can photoinhibit easier at levels when a fuller spectrum wouldnt).
For your tank, the 150s as 10,000Kish bulbs w/ blue+ T5s would be my suggestion. Its the most efficient light from both camps.
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"If at first, the idea is not absurd, then there is no hope for it" -Al Einstein |
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