# Comparing fluorescent lighting by type: T5HO vs. the rest

#### mathas

A trend I've seen lately when discussing lighting is to attribute some fairly impressive statistics to T5HO lighting; namely, that 1W used by a T5HO lamp results in twice the light output of 1W used by a normal fluorescent lamp (where "normal" could mean T5NO, T8, T12, or PC, depending on who's saying it). There's an old saying about things that seem too good to be true, and I wonder if this is another such case.

Here are a few examples of such claims that are directly quoted from threads here on FishLore:

The output of a T5HO light is approximately twice that of a T8 per watt. In other words 10w of T5HO light is about twice as intense/bright as 10w T8 light.
With T5 lighting, you cannot use the standard WPG formula. You need to basically double the WPG to get a better estimate on your lighting output.
T5HO lights have basically double the wattage of traditional fluorescent lights. So 100w of T5HO is like 200w of T8 or power compact.

So where does this belief come from? I'll freely admit, I use to parrot this belief as well; when I did so, I was saying it just because I'd read a lot of other people say it. Clearly, if many people say the same thing, it has to be true, right? Well, maybe not. The (or bandwagon mentality) can be a very real thing.

The more I learn about lighting, the more I find myself skeptical of this claim. The data I've found just doesn't support it. But before I dive into what data I have found, we need to understand how lighting is measured.

Since most of the lighting industry is concerned with humans, not plants, the output of most lamps is measured in lumens, which Wikipedia defines as "measure of the power of light perceived by the human eye". Luminous efficacy, then, is a ratio of lumens to power (in Watts). For example, an imaginary lamp that uses 100W and emits 5000lm has a luminous efficacy of 50 lm/W. Measuring light output in lumens really isn't ideal for those of us who are evaluating lamps based on benefit to plants, but it is the metric most readily-available, so this is how most lighting data is going to be presented.

The other (and more ideal for us) method of measuring light output is photosynthetically active radiation, or PAR. It's rare to find lamps with this information provided by the manufacturer, though, and most of this type of data is provided by hobbyists with PAR meters.

So now we have a common understanding of how lamp output is typically measured within the lighting industry. If we assume that the claims are true where a T5HO lamp does emit twice the light of a comparable "normal" lamp, there should be at least lumen measurements readily available to back this up. That doesn't seem to be the case. Here are examples of what I've found:

T8: 84 lm/W
T5: 89 lm/W
T5HO: 85 lm/W

T8: 80 lm/W
T5HO: 80 lm/W

T8: 89.1 lm/W
T5: 96.3 lm/W
T5HO: 86.1 lm/W

The National Lighting Product Information Program has comparison information at two different operating temperatures:

At 25ºC
T8: 90 lm/W
T5: 84 lm/W
T5HO: 75 lm/W

At 35ºC
T8: 83 lm/W
T5: 94 lm/W
T5HO: 85 lm/W

So far, you'll note that none of this information suggests that T5HO is anywhere close to twice the lumen output of a "normal" lamp per watt of power used. Specialty-lights.com does offer data that comes closer to suggesting this than the previous data, though their math is wrong:

Their Math
T8: 63 lm/W
T5HO: 92.6 lm/W

My Math
T8: 20000lm / 256W = 78.125 lm/W
T5HO: 20000lm / 216W = 92.6 lm/W

Now, earlier I said luminous efficacy probably shouldn't be our desired method of measuring light output. This is because lumens are adjusted for human vision; human photopic (daytime) vision is most sensitive to light at 555nm. If a lamp emphasizes this wavelength more than a different lamp with an identical length/power consumption, it will have a higher luminous efficacy. This does not necessarily mean the lamp emits more total light, merely that the lamp emits more of the light that our eyes are most sensitive to.

But what about PAR efficacy comparisons? PAR, like lumens, is a measurement of a specific subset of total emitted light. With PAR, it's the wavelengths plants need most (430-450nm and 640-660nm); with lumens, it's the wavelengths our eyes are most sensitive to (555nm). Again, a lamp with a higher PAR value than a similar lamp does not necessarily emit more total light, but it does emit more light that plants can use, which is probably of more importance to us as amateur aquatic gardeners.

I've only found one good data set so far that compares PAR/W efficacy, removed. Of all the lamps tested, the top ranking in both luminous efficacy and PAR/W efficacy was a T8 lamp.

And this makes sense to me; the wavelength of light emitted is dependent upon on the phosphors within the lamp (at least, when dealing with fluorescent lighting), not the diameter of the tube or the amount of power the ballast sends to the lamp. Some T5HO lamps may certainly be more photosynthetically efficient than some T8 lamps, but the reverse can also be true.

T5HO lamps absolutely, unquestionably provide more output per linear inch than normal T5 or T8, but that has nothing to do with efficiency. You can certainly get "more watts" in the same space using T5HO vs. T8, but again, that doesn't mean that each watt used results in a substantial increase in emitted light. T5HO (and T5NO), having a smaller diameter than T8, do tend to put more of the emitted light into the water than T8 when the reflectors used are designed well, but this "reflector factor", for lack of a better term, is unlikely to be anywhere near 1.5x-2x.

So yes, I do think that in practice, some T5HO bulbs are more efficient than some T8 bulbs. What I don't believe, yet, is that the increase is as drastic as a flat 1.5-2x increase across the board. Can anyone convince me?

#### A Sneaky Fatman

So let me see If I can even begin to explain what I'm thinking,

T5HO lights are not as "productive" as T8 lights on their own, but the ability to put more of them in a single area can increase the "density" of the lumens as percieved. Density of light particles, maybe?

And they are not as cost effective as the T8 bulbs?

And please excuse me if I sound like a total idiot. ;D

#### catsma_97504

OK, I think I'm starting to understand a few things that are leading to some of the confusion/miscommunication.

In the other thread where I stated that T5HO ran around 93 Lm/W. Further research is indicating that this is true of a 4-5 foot lamp, but many references appear to be referring to a 2-3 foot lamp.

Except from

54W T5 High Output 6500K Fluorescent Bulb
Brand Philips, GE or Sylvania
Watts 54
Initial Lumens 5,000
Mean Lumens 4,700
CRI 85
Kelvin Temp. 6500°K (Cool)

This would indicate that a new bulb runs at 92.6 Lm/W and will average 87 Lm/W during the life of the bulb.

Except from

24W T5 High Output 6500K Fluorescent Bulb
Brand Philips, GE or Sylvania
Watts 24
Initial Lumens 2000
CRI 85
Kelvin Temp. 6500°K (Cool)

This 24 inch T5HO lamp indicates it will initially run at 83.3 Lm/W. And, if we assume it will also lose 6% of its luminosity over the life of the bulb (percentage of loss in the 4 foot lamp), it would average 78.3 Lm/W during the life of the bulb.

Mathas quoted ratings from at 80 Lm/W for T5HO lighting. However, I do not find the length of the bulb they are describing in the PDF file. This apparently important piece of information is missing. Knowing that a 2 foot T5HO lamp runs in the low 80s Lm/W, I can only assume this is what they are referring to and not to a 4-5 foot lamp that typically runs at a higher Lm/W.

With this information, my conclusion is that different sources are referring to different length of bulb lending more confusion to this subject.

And, what about other factors the can affect efficacy? How about the reflectors in the fixture? Some fixtures are not as reflective leading to loss of potential lighting. This information appears to be missing from the documentation available to us. Do we take this at face value and assume a true scientific study was undertaken and also assume that the same fixture was used for the studies? If we are looking at specifics, then this becomes a factor in the reported findings.

And to be honest, CRI ratings are lost on me still. But, that is yet another topic.

#### A Sneaky Fatman

You don't sound as lost as I did

#### mathas

T5HO lights are not as "productive" as T8 lights on their own, but the ability to put more of them in a single area can increase the "density" of the lumens as percieved. Density of light particles, maybe?
I wasn't necessarily trying to say that T5HO is less efficient than T8, or less productive, or less anything.

Rather, I'm trying to understand why so many people seem to feel that, watt for watt, T5HO offers twice the output of "normal" fluorescent lighting when there doesn't seem to be a lot of data readily available to support the claim.

And they are not as cost effective as the T8 bulbs?
I left cost out of the discussion on purpose

Does a 4' T5HO lamp cost more than a T8 lamp? Yes.
Does a 4' T5HO lamp emit more light than a T8 lamp? Yes.
Which is more cost-effective? It depends.

And, what about other factors the can affect efficacy? How about the reflectors in the fixture? Some fixtures are not as reflective leading to loss of potential lighting. This information appears to be missing from the documentation available to us. Do we take this at face value and assume a true scientific study was undertaken and also assume that the same fixture was used for the studies? If we are looking at specifics, then this becomes a factor in the reported findings.
If this whole theory is based on most T8 fixtures having poor or no reflectors and most T5HO fixtures having well-designed reflectors, then that would answer my question. It would just be less-than-optimal wording on the part of the people repeating the theory; they don't actually mean that T5HO lamps emits twice the light per watt used, but rather than most T5HO enclosures are better at redirecting the light that is emitted into the water. I would agree with this as a concept, with the caveat that the same reflector design applied to a T8 enclosure should close the perceived gap significantly.

But as long as you're wondering about other factors that are involved, you can also include variance in the specific ballasts used, the fact that each individual lamp has its own luminous efficacy and PAR/W efficacy that is completely independent of what diameter the lamp is, the fact that T5HO and T8 have differing rates of luminous degradation (meaning the comparison values on day 1 won't match the comparison values on day 180), etc.

There are just so many factors involved that I cannot understand the claim that T5HO offers twice the output per watt used as "normal" fluorescent lighting across the board, unless it's confusion about reflectors as noted above. At times T5HO might be more efficacious, at other times it might not be; and my hunch is that the difference will depend strongly on which phosphors the manufacturer used in the lamp, not just the diameter or length of the lamp.

#### Kunsthure

I don't have time to really read through the links right now but I see what you're saying. I have read several articles with the same idea, that light output should be measured in everything but watts to get a more accurate measurement. However, that doesn't change the fact that most of us still think in watts because that's what we're familiar with. A 15w bulb is not as bright as a 30w bulb, that's what we all learned as a child and it makes perfect sense.

So my question for you is, keeping in mind that most of us only do/want to think in watts: then how does T5HO lamp wattage compare to T8? Because we do know that a 30w T8 lamp does not have the same brightness as a 30w T5HO. What am I supposed to tell someone new to lighting who's already confused by terms like "T8" and "WPG"?

-Lisa

ps. I appreciate the work you put into this post, maybe it should be stickied.

#### mathas

So my question for you is, keeping in mind that most of us only do/want to think in watts: then how does T5HO lamp wattage compare to T8?
My guess is that their output is probably pretty close, watt for watt, if you're looking at total emitted light. Some T5HO ballast/lamp combinations at certain temperatures will produce more output per watt than some T8 ballast/lamp combinations, and vice-versa.

The really tricky part is that it's quite hard to accurately compare the two types watt for watt. A 4' T5HO lamp typically uses 54W, while a 4' T8 lamp typically uses 32W; they're just not the same thing. This difficulty in accurately comparing the two is where the luminous efficacy and PAR/W efficacy ratios come into play, and the data of this type that I've been able to find puts them relatively close to one another.

One point that's definitely in favor of T5 and T5HO is that the smaller lamp diameter reduces the chance of restrike (light bouncing off the reflector and hitting the lamp again, rather than being redirected outward/downward). This does, in theory, give a slight nod to T5 and T5HO over T8/T12 with regards to how much of the emitted light makes it into the tank, but I'm still skeptical that's anywhere near as dramatic as a 2x increase when comparing apples to apples.

Because we do know that a 30w T8 lamp does not have the same brightness as a 30w T5HO.
There are a couple of problems with this conclusion:

1. "Brightness", as alluded to earlier, is at least partially a function of human spectral sensitivity. There are 30W T8 lamps that we interpret as brighter than other 30W T8 lamps simply by virtue of which wavelengths of light the phosphors in the lamp emphasize.

2. T5HO has a higher output per inch. Assuming you found a T5HO lamp that used exactly as much power as a T8 lamp, the T5HO lamp would be shorter; therefore, the emitted light would be concentrated over a smaller space. This does not necessarily imply it produces more or less light per watt used, just that the light produced is more concentrated.

What am I supposed to tell someone new to lighting who's already confused by terms like "T8" and "WPG"?
That's a great question, and one I don't have an answer for. Lighting is an extremely complex topic, with many concepts building on other concepts, and I'm not sure how best to make it palatable for newbies.

My personal stance is to do my best to answer the question asked. If my answer goes over the poster's head, hopefully they'll ask clarifying questions about the part or parts they don't understand.

#### Kunsthure

How is it that the T5 has higher lm/w than T5HO? I thought the whole point of the HO was to have a higher output that T5, y'know, hence the name?

Why do plant people say their plants do better under T5HO or even T5 than T8? Is it just that T5HO is the cool new thing so everyone wants it?

And what's the bottom line, should people (ie me) buy T8, PC, T5 or T5HO for a high light tank?

-Lisa

#### catsma_97504

The really tricky part is that it's quite hard to accurately compare the two types watt for watt. A 4' T5HO lamp typically uses 54W, while a 4' T8 lamp typically uses 32W; they're just not the same thing. This difficulty in accurately comparing the two is where the luminous efficacy and PAR/W efficacy ratios come into play, and the data of this type that I've been able to find puts them relatively close to one another.

A thought crossed my mind while reading this. If a typical 4 foot T8 lamp runs at 32W and a typical 4 foot T5HO lamp runs at 54W, could it be as simple as the fact that T5HO offers 40% more wattage and therefore will have a higher output? 40% increase is a far cry from double, but it may be part of the answer. I know I'll never tell someone to double their wattage to estimate how much light they have available for plants.

I need to study up on PAR and CRI....they are still a confusion topic for me. I know that the ballasts are different and that T5HO typically has improved reflectors when compared to T8/T12, not to mention reduced restrike due to the smaller diameter of the tubes, differences between phosphors, air temp, etc. The more I learn in regards to aquarium lighting, the less I understand it. To say it is a confusion subject is an understatement.

#### mathas

How is it that the T5 has higher lm/w than T5HO? I thought the whole point of the HO was to have a higher output that T5, y'know, hence the name?
Please don't confuse output with efficiency. "Output", for us, is measured in lumens or PAR; those measurements will be higher for T5HO.

What I'm questioning is the claims of increased efficiency, not output.

Why do plant people say their plants do better under T5HO or even T5 than T8? Is it just that T5HO is the cool new thing so everyone wants it?
I have no idea why anybody does anything

My guess is when these people switch from T5 or T8 to T5HO, they're likely getting a pretty dramatic increase in total emitted light. Most T8 fixtures I've seen are limited to 1 or 2 lamps, while T5HO can go from 2-8 lamps per fixture.

And what's the bottom line, should people (ie me) buy T8, PC, T5 or T5HO for a high light tank?
Whatever you want.

If your goal is to get as much light as possible in a given space, go T5HO. If your goal is to reach a specific lighting threshold as efficiently as possible, I'm not sure there is a big difference between any of the fluorescent types.

If a typical 4 foot T8 lamp runs at 32W and a typical 4 foot T5HO lamp runs at 54W, could it be as simple as the fact that T5HO offers 40% more wattage and therefore will have a higher output?
If you changed "T5HO offers 40% more wattage" to "T5HO uses 40% more power" (watts are a measurement of power, not of light), you'd have exactly the point I've been not-so-successfully trying to make. If you use more power, you get more output. This is not necessarily an increase in efficiency.

The more I learn in regards to aquarium lighting, the less I understand it. To say it is a confusion subject is an understatement.
Welcome to the club, it doesn't get any better the more you think you learn

#### Paigee

I just bought what my fav LFS owner told me to It ended up being a T5HO. I like it

#### catsma_97504

If you changed "T5HO offers 40% more wattage" to "T5HO uses 40% more power" (watts are a measurement of power, not of light), you'd have exactly the point I've been not-so-successfully trying to make. If you use more power, you get more output. This is not necessarily an increase in efficiency.

Welcome to the club, it doesn't get any better the more you think you learn

That's what I was trying to get at. More wattage equates to more lighting and therefore must indicate more efficiency. Right arty0009:

#### A Sneaky Fatman

I believe a light that uses more watts would yield an increase if efficacy, not efficiency

Efficacy deals with the ability to put out more light

Efficiency deals with the ability to put out more light, with less watts/energy.

Correct me if i'm wrong.

#### mathas

I believe a light that uses more watts would yield an increase if efficacy, not efficiency

Efficacy deals with the ability to put out more light

Efficiency deals with the ability to put out more light, with less watts/energy.

Correct me if i'm wrong.
Based on what the words efficacy and efficiency mean outside the realm of lighting, I would agree. For some reason, though, once people start talking about lighting, it gets really confusing. I tend to use them interchangeably without even realizing I'm doing it.

The best I can do to answer this is to quote Wikipedia:

Efficacy and efficiency

In some other systems of units, luminous flux has the same units as radiant flux. The luminous efficacy of radiation is then dimensionless. In this case, it is often instead called the luminous efficiency or luminous coefficient and may be expressed as a percentage. A common choice is to choose units such that the maximum possible efficacy, 683 lm/W, corresponds to an efficiency of 100%. The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

#### Nate McFin

Very good thread, thanks for the info.
As a side note I would also like to add that setting a T5Ho directly on top of the tank will most likely cause algae problems even with Co2 and Ferts being added. Here is an interesting thread started by Hoppy on planted tank that I found very interesting. It served as the model for how I setup my 40 Breeder tank.

Please note that PAR not watts per gallon is what is used here. Watts per gallon in my opinion is nearly useless. Choose a light and determine how to set it up properly. Allow for room to move up and down as well as adjusting the duration. This chart will work great for those trying to find the proper DISTANCE (not WPG!) to set the light up for the type of tank they want. (low-medium-high)

#### mathas

Here is an interesting thread started by Hoppy on planted tank that I found very interesting. It served as the model for how I setup my 40 Breeder tank.
Thanks for sharing, Nate!

It makes me feel a lot more confident that I'm not just missing something really obvious if Hoppy is saying the same thing I am (post 9, specifically). I think he's probably forgotten more about lighting this month than I've ever known.

#### Kunsthure

Please don't confuse output with efficiency. "Output", for us, is measured in lumens or PAR; those measurements will be higher for T5HO.

When I see "efficient" in relation to anything electrical, I think "doing the same with less electricity." Maybe that's the tree hugger in me trying to reduce my carbon footprint, or maybe that's just my poor understanding of electrical engineering, or both. So I've been interpreting efficiency in lighting as using fewer watts to have the same output. Is that incorrect?

ETA: I'm now just as confused about lighting as I was when I first started. So someone please just tell me what I need to buy to have a high light 75 gallon tank.

-Lisa

#### mathas

When I see "efficient" in relation to anything electrical, I think "doing the same with less electricity." Maybe that's the tree hugger in me trying to reduce my carbon footprint, or maybe that's just my poor understanding of electrical engineering, or both. So I've been interpreting efficiency in lighting as using fewer watts to have the same output. Is that incorrect?
Your understanding of efficiency is correct.

The question I was responding to in the post you quoted was "How is it that the T5 has higher lm/w than T5HO? I thought the whole point of the HO was to have a higher output that T5". That's the quote where it sounded like you might have been confusing efficiency with output. Lumens per watt is a measure of efficiency, while "HO" signifies higher output. Something can have a higher output without being more efficient; think V8 engines vs. hybrid engines. The V8 will have a higher total horsepower output than the hybrid, but the hybrid will use less gasoline achieving the same speeds. That's not a perfect metaphor, but hopefully it's close enough.

Look at the quotes from other FL members I had in my original post. Statements like "the output of a T5HO light is approximately twice that of a T8 per watt" and "100w of T5HO is like 200w of T8 or power compact" are claims that T5HO is twice as efficient as T8, claims for which I have seen no supporting data.

#### Kunsthure

Look at the quotes from other FL members I had in my original post. Statements like "the output of a T5HO light is approximately twice that of a T8 per watt" and "100w of T5HO is like 200w of T8 or power compact" are claims that T5HO is twice as efficient as T8, claims for which I have seen no supporting data.

As one of the people who has been saying that 100w of T5HO is like 200w of T8, I don't intend that statement to mean that a T5HO is more efficient, meaning uses less electricity for the same watts of T8 (though I guess in the mathas way of talking about lighting, technically that's what I'm saying ). What I'm intending to say, and what I think most newbies interpret it as, is that the output of a T5HO is higher than a T8, as in it's "brighter" or "more powerful." Like I mentioned in my first post, the average person thinks of output as watts because that's how bulbs are marketed. I bet if you asked someone who knows nothing about lighting how a 10w bulb compares to a 75w bulb, s/he is going to say that the 75w is "brighter." And since WPG is one of the first things someone new to lighting encounters, knowing how many watts a bulb is tells them how "bright" the bulb is.

Now as for how accurate the idea that a T5HO bulb is twice as "bright" (meaning twice the output and therefore increased WPG in newbie-speak), I really have no idea. I think it was Nutter that I first saw stating the twice-the-output idea, so you can blame him for the misinformation I've been spreading.

I know that to you technical types, WPG is meaningless, but humor me please. . How does a 100w T5HO compare to a T8 bulb when figuring out WPG?

Oh, and has anyone here used the AH Supply Bright Kits mentioned in the link to plantedtank? If I can get more output for less money, I'm all for it.

-Lisa

#### Kunsthure

To quote Hoppy from that thread on plantedtank:
I do know that T5NO lights are more efficient than T5HO - more light per watt - and T5NO lights are a bit more than half the wattage of T5HO lights. So, a T5NO light should produce more than half the light that a T5HO light does

Ok, maybe (probably) I'm a little dense, but isn't Hoppy saying the same thing you've been working to dispel, mathas? Isn't he saying that 100w of T5NO would be equivalent to about 200w of T5HO, and that a T5HO is about twice as "bright" (aka output) as a T5NO?

-Lisa

#### mathas

As one of the people who has been saying that 100w of T5HO is like 200w of T8, I don't intend that statement to mean that a T5HO is more efficient, meaning uses less electricity for the same watts of T8 (though I guess in the mathas way of talking about lighting, technically that's what I'm saying ). What I'm intending to say, and what I think most newbies interpret it as, is that the output of a T5HO is higher than a T8, as in it's "brighter" or "more powerful."
I agree with the intent, a T5HO lamp of a given length is going to have a higher output than a T8 lamp of the same length. If the premise were "1 T5HO lamp provides similar output to 2 T8 lamps", I might agree, but that's not what's being said. When someone specifically says that 100W of power used by one type of lamp is equivalent to 200W used by another type, that is a claim of increased efficiency, regardless of what's intended. That is what I'm asking to see supported with evidence.

Hopefully no one thinks I'm picking on you personally. You're by no means the only one I've seen repeat this claim, you're just the only I've seen do so that's actually responding to this thread. I'm really trying to understand where this idea comes from, and I'm still holding out hope that someone will chime in with evidence or an explanation of some sort that gives me an "AHA!" moment.

But your explanation, assuming I'm understanding you correctly, that "100W T5HO = 200W T8" isn't meant to be taken literally does clear up some of my confusion; I read it literally. My posts in this thread (including the remainder of this one) are responding to the literal statement, not the intent behind the statement.

Like I mentioned in my first post, the average person thinks of output as watts because that's how bulbs are marketed. I bet if you asked someone who knows nothing about lighting how a 10w bulb compares to a 75w bulb, s/he is going to say that the 75w is "brighter." And since WPG is one of the first things someone new to lighting encounters, knowing how many watts a bulb is tells them how "bright" the bulb is.
Ok, let's assume newbies think that "more watts = brighter" (which I would tend to agree with under most circumstances). That's a decent starting point.

So starting with "more watts = brighter", it makes sense to say that a 54W T5HO lamp would be brighter than a 32W T8 lamp. How do we jump from that point to "100W T5HO = 200W T8"?

I think it was Nutter that I first saw stating the twice-the-output idea, so you can blame him for the misinformation I've been spreading.
Oh, Nutter and I have debated this before in private messages We both looked at the same data (the NLPIP study linked to in the first post) and each interpreted it differently.

I know that to you technical types, WPG is meaningless, but humor me please. . How does a 100w T5HO compare to a T8 bulb when figuring out WPG?
That depends.

If you mean "How does 100W T5HO compare to 100W T8 when figuring out WPG", then the answer is "equal" assuming the same tank is used. If a ratio uses watts and gallons, lamp diameter is irrelevant: 100/x = 100/x.

On the other hand, if you mean "How does a 100W T5HO lamp compare to a T8 lamp of the same length when figuring out WPG", then the answer is "higher". As an example, let's think of a 48" 55 gallon tank with a one-lamp fixture.

A 48" T5HO lamp uses 54W
A 48" T8 lamp uses 32-40W

T5HO: 54W / 55 gallon = .98 WPG
T8: 32W / 55 gallon = .58 WPG
T8: 40W / 55 gallon = .73 WPG

None of this, however, has anything to do with the claim that "100W T5HO = 200W T8".

Oh, and has anyone here used the AH Supply Bright Kits mentioned in the link to plantedtank? If I can get more output for less money, I'm all for it.
I use them, and they're awesome. The most important thing to know is that you get a ballast, endcaps, reflectors, and wiring; you're responsible for the bulbs and the enclosure (though you can buy them from AHSupply if you choose) and you're responsible for the assembly. The directions are quite good, and I'm certain KI'm would be willing to answer any questions you had along the way if you called him. As long as you don't panic when you open the package, take it slow, follow the directions, and aren't colorblind, it's not too hard to assemble.

And Kim's customer service is great if you run into problems or have questions; I received a faulty endcap in my order, and within an hour of getting off the phone with him I already had a UPS tracking number for my replacement part.

Ok, maybe (probably) I'm a little dense, but isn't Hoppy saying the same thing you've been working to dispel, mathas? Isn't he saying that 100w of T5NO would be equivalent to about 200w of T5HO, and that a T5HO is about twice as "bright" (aka output) as a T5NO?
Maybe it's a matter of selective interpretation, but I would say he's agreeing with me. Hoppy says in that post that "T5NO lights are more efficient than T5HO - more light per watt". The point I've been trying to make is that I've seen no proof that T5HO is twice as efficient as other lighting types, and he said flat out that they are less efficient than normal T5.

#### Kunsthure

I have tried twice now to write this post and the first time, FL sabotaged me and the second was my iPod. Maybe it's a sign.

I know you're not picking on me, mathas. As for why I'm the only one who has given the double output info who is also responding to this thread, I have no idea. Maybe it's because no one likes to find out someone else thinks they're wrong. And there's little sense in us mortals trying to debate you on the topic of lighting. ;p

I've realized that we've been talking about the same topic, but not the same subject while thinking the other was talking about the same subject. If that mad any sense. You're focused on efficiency and I'm focused on output, and you've been thinking from an electrical engineering focus while I've been thinking from an explaining-it-to-newbies focus.

What you and I need to do is come up with a way to explain lighting to newbies in simple terms that they won't gloss over like I did, yet satisfies your semantics issues. ;p I've toyed with writing a intro to lighting, part glossary and part guide. I also toyed with working on that tonight but then stuff and things occurred and happened and uh kind of distracted me. But maybe I'll get a chance this weekend and I'll PM it to you so you can tell me how wrong I am.

So to recap: we're both right.

-Lisa

#### catsma_97504

As efficiency and efficacy are not the same thing, we are only furthering this confusion within our own conversation here.

So, I thought I'd referr to the WikI articles on Efficacy and Luminous Efficacy.

In lighting design, "efficacy" refers to the amount of light (luminous flux) produced by a lamp (a light bulb or other light source), usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts.

Efficacy would be the lumens per watt ratio. {Efficacy = lumens / watts}

This is not to be confused with efficiency which is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible power as a fraction of the power consumed in watts.

Efficiency is a measurement of energy consumed when compared to output lighting. It is a dimensionless ratio, so how in the world are we supposed to measure it? The only thing I am confident about is that efficiency is a percentage and it is not a measure of Lumens per Watt.

The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

"Not always carefully maintained in published sources" - talk about an understatement!

Putting that aside, we are still at Efficiency = dimentionless percent and Efficacy = Lumens / Watt.

Lumens per watt is a measure of efficiency

This is not a true statement. Lumens per watt is a measure of efficacy.

Maybe it's a matter of selective interpretation, but I would say he's agreeing with me. Hoppy says in that post that "T5NO lights are more efficient than T5HO - more light per watt". The point I've been trying to make is that I've seen no proof that T5HO is twice as efficient as other lighting types, and he said flat out that they are less efficient than normal T5.

I believe we can all agree that T5HO has a higher Lumen to Watts ratio. Therefore, it does have a higher efficacy and produces a greater amount of light. If we replace the word "efficient" with "efficacy", then then above statement would be accurate.

We need to be cognizant of the blurry line that separates efficacy and efficiency when discussing lighting. To say that T5HO is close to double is an accurate statement for efficacy, not for efficiency. T8 can produce 2,700 Lumens of light and T5HO can produce 5,000 Lumens of light when both tubes are new. This does lend itself to the fact that T5HO is close to double the Lumen output of a T8 tube that is the same length because a T5HO lamp can produce the same amount of Lumens with approximately half the required wattage.

The output of a T5HO light is approximately twice that of a T8 per watt. In other words 10w of T5HO light is about twice as intense/bright as 10w T8 light.
This statement would be partially accurate if you replaced the word "output" with "efficacy". The reason T5HO appears brighter to our eye is because it has a higher efficacy.

T5HO lights have basically double the wattage of traditional fluorescent lights.
This is an accurate statement when comparing same length bulbs for efficacy. Although in reality it is not a true double, but more like a 60% gain in efficacy when comparing T8 with T5HO.

When discussing lighting with a newbie, we need to be aware of this difference. T5HO has a higher efficacy per watt and will therefore produce more overall light when compared watt for watt with a standard T8 bulb of the same length.

I have not been discussing lighting efficiency. However, I believe is Mathas is. I do not believe a lamps efficiency is in question as Mathas has clearly made his point on this subject. It is not, however, an indicator of efficacy. And, these terms should not be used interchangeably.

#### mathas

I believe we can all agree that T5HO has a higher Lumen to Watts ratio.
We can?

Unless I missed a post somewhere, every datapoint provided so far in this thread, with the exception of specialty-lights.com, has T5HO losing in lumen/watt comparisons to T5NO, and on par with or losing to T8. If you have data that clearly puts T5HO significantly in the lead, please share... that's what I've been asking for all along.

Efficiency is a measurement of energy consumed when compared to output lighting. It is a dimensionless ratio, so how in the world are we supposed to measure it? The only thing I am confident about is that efficiency is a percentage and it is not a measure of Lumens per Watt.
While you are correct, I would argue that efficacy is a reasonable analogue for efficiency, as far as discussion within this hobby goes. If we were authoring theses or scholarly articles for publication, it would be a much more important distinction.

#### catsma_97504

We can?

Unless I missed a post somewhere, every datapoint provided so far in this thread, with the exception of specialty-lights.com, has T5HO losing in lumen/watt comparisons to T5NO, and on par with or losing to T8. If you have data that clearly puts T5HO significantly in the lead, please share... that's what I've been asking for all along.

In an earlier post, you stated:

My Math
T8: 20000lm / 256W = 78.125 lm/W
T5HO: 20000lm / 216W = 92.6 lm/W

In a watt for watt comparison, T8 produces less light than a T5HO lamp. For each watt of energy T5 is 15% more efficacious and will produce 15% more light. In other sources, I've seen a higher difference when comparing T8 to T5HO.

100W T8 will produce 781.25 Lumens and the same 100W T5HO will produce 926 Lumens.....using your math. More lumens = more light with the same amount of energy (watts consumed). Does that make the T5HO lamp more efficient?

#### mathas

n a watt for watt comparison, T8 produces less light than a T5HO lamp. For each watt of energy T5 is 15% more efficacious and will produce 15% more light. In other sources, I've seen a higher difference when comparing T8 to T5HO.

100W T8 will produce 781.25 Lumens and the same 100W T5HO will produce 926 Lumens.....using your math. More lumens = more light with the same amount of energy (watts consumed). Does that make the T5HO lamp more efficient?
According to that one source, yes. What about the other sources that offer contradictory information?

#### Kunsthure

Can we stop with the long posts? It's a real PITB to scroll through the page on my iPod. Break them up into shorter posts so we can have more pages. I know that contributes nothing to the argument, I just feel left out now that mathas has stopped picking on me.

I think we need to focus on efficacy rather than efficiency here. We've established the efficiency (or at least I think we have?). But what's at the heart of these claims of double the wattage is efficacy, because the analogy is made to help newbies understand the difference in brightness (efficacy, yes?) between T5HO and traditional T8. It seems that mathas is the only [vocal] one to be taking "watt" literally, when what the claim is about is the efficacy (output, "brightness") of the bulbs.

-Lisa

#### bubblynutter

I have nothing constructive to add to this discussion, I just wanted to let everyone know how I found this thread and why I found it useful!

I am in the market for new lighting, and have been toying with the idea of T5HO, but not really sure if I was getting the right thing. I was under the misconception of T5HO = twice the efficiency of T5NO. I decided to search high output lighting on fishlore and came across this thread.

The bad news is I am still not sure if I will get T5HO over T5NO, as it will increase my already large power bill. :shock: But I hope this discussion does not end here, as I have found it thoroughly informative and useful to read through.
It made me realise I have a lot more reading to do on the matter before purchasing new lights!

Please keep this thread going, as I believe it to be very useful on the horridly confusing topic of aquarium lighting.

Replies
3
Views
439
KeeperOfASilentWorld
Replies
6
Views
2K
DrTim
Replies
6
Views
419
TexasDomer
• JustAFishServant
• Lighting
Replies
6
Views
168
MacZ
Replies
14
Views
589
Thunder_o_b