Key takeaways
- The four 8-lamp fixtures drew between 393 W and 458 W at the wall — a 16.5% spread before a single PAR reading was taken.
- Centre intensity ran from 295 to 360 µmol/m²/s at 24 inches, a 22% gap that tracks the wattage gap almost exactly.
- On PAR per watt all four fixtures land within 4% of each other, so the brightest unit is the one drawing the most power rather than the one converting it best.
- Every footprint spread light further across the fixture than along it, so fixtures should overlap end to end rather than side by side.
- Corner readings on a 5 x 5 came in under 50 µmol/m²/s on all four units, which is what makes T5 a veg and propagation light rather than a flowering one.
Hello my fellow growers — Nate here. T5 high output fluorescent does not get much attention next to modern LED grow lights, but it is still the thing a lot of growers reach for over a clone tray or a bench of young plants. So we put four 4-foot, 8-lamp T5 HO fixtures on the meter, moved the same bulbs between them, and mapped every footprint.
The numbers below are the full set: wall volts, amps and watts for each unit, a 41-point PAR grid across a 5 x 5 area, and what those two things say about each other. The short version is that these fixtures are far more alike than their badging suggests, and the one difference that matters is not the one most growers look at.
Video transcript about 6 minutes
0:12Hello my fellow growers, Nate here, and we're just finishing up doing a new test that we're going to post that I was very excited about, even though they might not be considered the coolest lights in the industry: T5s. Four-foot, eight-bulb high output T5 fixtures.
0:31We've been wanting to do this test internally for a long time, because there are tons of people that ask us which T5 is best, which is the best one to use, which one gives you the best spread output. And we finally got all the lights in house, ripped them out of the boxes, threw them under our lighting footprint, the 5x5. And what we did was essentially put the same bulbs in four different T5 fixtures. We used the Grow Crew four-foot eight-bulb T5 fixture, the EnviroGro four-foot eight-bulb T5, the Sun Blaze, and the Quantum four-foot.
1:12So we had our suspicions of which fixture would do best, and you'll see in the testing below that the Quantum fixture actually has a really, really awesome spread. But the things to really watch out for is that there's different scenarios for these T5s that could make them have, you know, maybe higher output. But we also noticed that the ballast driving them were also running a higher wattage. So we actually did some of our own calculations to figure out what we considered, you know, an efficiency ratio, and you'll see those in the PDF that you can click on below.
1:54But I mean, by looking at this testing you can really see, you know, exactly how much wattage these fixtures are drawing from the wall, exactly what the amperage is, exactly what the footprint is. And really the only difference in these fixtures is that they have different ballasts and they have different reflectors. But we used the same exact bulbs for each fixture. We just took the bulbs out of one fixture, put them in the next, so that we can keep that variable held constant. And these are in the exact same space using all the exact same power. So the test is very enlightening, if I do say so myself.
2:30If you have any feedback, leave it in the comments below. We're also going to be testing out T5 bulbs here in a second, especially with the introduction of the new Hortilux PowerVEG T5, so keep an eye out for that. For that we'll change out a whole bunch of different T5 bulbs in the same fixture to see which T5 bulbs are really the best ones.
2:51So use these fixtures, you know, for vegetative growth primarily. And, you know, seeing which fixture had the best spread really helps us figure out how we can put these fixtures in our vegetative growth areas so that we have good even light coverage, and we're getting the most out of those T5 fixtures. This is Nate from Growers House.
3:15So first off, before we get into showing you the PAR difference of the fixtures, I wanted to show you guys the spectral output of a T5 high output light. Now, looking at this spectral graph, this is actually a 6500 Kelvin bulb, and you can see that the spectrum is relatively broad actually. You've got reds, yellows, even some greens, blues and some deep blues. So this is what the spectral graph looks like of a high output 54-watt T5 bulb.
3:49Now jumping into the fixtures, you'll notice basically every PAR footprint, the intensity is a little bit more uniform wide than it is long. And that's to be expected with these fixtures, because the reflector kind of diverts the light to go left and right rather than the long way. So wide instead of long. Which this is a really good fact to know, because it can help out in mapping your grow room. You don't need as much cross lighting going sideways from the fixture as you do longitudinally.
4:21So, stacking these fixtures up against each other, you can see that there wasn't a huge variance. I mean, we're probably talking, you know, especially when you talk about the outside perimeter, we're only talking about maybe a difference of about 10%. But once you get towards the center, I mean, the difference between the least intense and the most intense unit is about 20%, from the Grow Crew to the Quantum BadBoy.
4:48But other than the Quantum BadBoy, the fixtures were pretty similar. Like the EnviroGro, Sun Blaze and Grow Crew fixture were all kind of neck and neck. It depends on which area you measure and which fixture does best. But the BadBoy stood out quite a bit, and I think that's because the ballast is driving more wattage to the bulbs, and the reflector is actually larger, and the reflective material inside of it seems to be of higher quality.
5:15And you'll even notice there's kind of an arbitrary ratio that we came up with, but take it for what you will. We wanted to show it off anyways. It's the PAR over watts ratio. We took the total PAR divided by the watts to give you a ratio, essentially, that's, you know, I guess you can consider it somewhat of an efficiency ratio, or like how much light output you're getting per watt.
5:39And you'll notice that the Quantum again did best out of all these fixtures. So if you're looking for the best, you know, unit out there, I'd say the Quantum BadBoy is definitely it. Other than that, this is Nate from Growers House. Stay tuned for more tests. Happy growing.
Where T5 still earns its place
T5 HO lost the flowering argument years ago and is not coming back to it. What it kept is the job it was always good at: a wide, soft, low-heat blanket of light a few inches above small plants, with no ducting, no ballast box and nothing to burn a cutting that drifts too close.
Clone domes, seedling benches, mother plants and the first two weeks of veg all want the same thing — even coverage at low intensity, close to the canopy. A tube does that naturally because the emitting surface is four feet long instead of a point. The trade is efficiency: a modern LED bar puts far more photons on the same bench for the same power, which is why the propagation LED comparison is worth reading beside this one.
Where T5 still wins outright is cost of entry and cost of repair. A tube is a few dollars and swaps in ten seconds; nothing is soldered, nothing is proprietary, and a failed lamp does not take the fixture with it.
How we ran the test
The whole point of the exercise was to isolate the fixture, so the bulbs were held constant. We ran the same T5 HO 6500K lamps in every unit, physically moving them from one fixture into the next rather than trusting that two sets of tubes were identical.
That leaves the ballast and the reflector as the only variables, which is what a fixture comparison should be measuring. Everything was tested in the same room on the same circuit, mapped over a 5 x 5 foot area, with every PAR reading taken at 24 inches below the fixture. We also logged volts, amps and watts at the wall for each unit, which turned out to matter more than anything else we recorded.
Four fixtures went through it: the EnviroGro 4 ft 8-bulb, the Sun Blaze 4 ft 8-lamp, the Quantum BadBoy 4 ft 8-bulb and the Grow Crew 4 ft 8-bulb.
What the four fixtures measured
All four are sold as 8-lamp T5 HO fixtures running eight 54-watt tubes, which implies 432 watts of lamp load. None of them drew that, and the spread between them is wider than anything in the light readings.
| Fixture | Volts | Amps | Watts | Centre PPFD | Sum of 41 readings |
|---|---|---|---|---|---|
| Quantum BadBoy 4 ft 8-bulb | 120.0 V | 3.84 A | 458 W | 360 | 6,950 |
| EnviroGro 4 ft 8-bulb | 120.3 V | 3.70 A | 446 W | 315 | 6,505 |
| Sun Blaze 4 ft 8-lamp | 120.6 V | 3.53 A | 396 W | 300 | 5,945 |
| Grow Crew 4 ft 8-bulb | 119.4 V | 3.47 A | 393 W | 295 | 5,915 |
Lowest to highest is 393 W against 458 W — a 16.5% spread on four fixtures that all claim the same lamp count and the same lamp wattage. That is the ballast making its own decision about how hard to drive the tubes. It is not a fault; it is a design choice, and it is invisible unless somebody puts a meter on the cord.
Readings are in micromoles per square metre per second. The sum column adds the 41 points mapped across the 5 x 5 grid, which is the number the next two sections turn on.
Reading the PAR footprints
Centre intensity ran from 295 to 360, a 22% gap. Set that beside the 16.5% wattage gap and most of the difference is already explained: the fixture pulling the most power put the most light on the bench.
The edges tell a flatter story. Mid-edge readings land between 100 and 130 across all four units, and every corner on every fixture came in between 20 and 25. No 8-lamp T5 HO fixture in this test put more than 50 µmol/m²/s into the corner of a 5 x 5 at 24 inches.
That corner number is the honest limit of the format. It is plenty for cuttings under a dome and fine for seedlings; it is nowhere near a flowering canopy, and no reflector design on the list changes that. If the plan is to flower under this footprint, the answer is a different technology rather than a different T5.
PAR per watt
Raw brightness is the easy comparison and the least useful one, because it rewards the fixture that draws the most power. The question worth asking is how much light each unit returns for every watt it pulls, and that is a straight division: total the 41 PAR readings across the footprint, divide by the measured wall watts.
Run that on all four and the results sit remarkably close together.
| Fixture | Sum of 41 readings | Wall watts | PAR per watt |
|---|---|---|---|
| Quantum BadBoy | 6,950 | 458 W | 15.17 |
| Grow Crew | 5,915 | 393 W | 15.05 |
| Sun Blaze | 5,945 | 396 W | 15.01 |
| EnviroGro | 6,505 | 446 W | 14.59 |
The four fixtures span 14.59 to 15.17 — a 4% spread. On this measure they are, for practical purposes, the same fixture. Reflector shape, housing material and ballast brand all vary between them, and none of it moves the efficiency needle by an amount a grower would ever notice.
Which puts the brightness ranking in its proper place. The BadBoy does put the most light on the bench, and it does it by drawing 65 more watts than the Grow Crew. That is a ballast tuned to run the tubes harder, not a fixture that does more with less. Run the BadBoy and you get more light and a bigger power bill in roughly equal measure.
The useful version of this is a rule of thumb: check the wall draw first. Two 8-lamp T5 fixtures quoting the same lamp count can sit 65 watts apart, and that one number predicts the PAR difference better than any reflector claim on the box.
Wide beats long
One pattern showed up in all four footprints and it is the most useful thing in the whole dataset. Intensity falls away faster along the length of the fixture than it does across the width.
Take the BadBoy grid as the example. Moving sideways from centre, readings go 360, 350, 305, 250, 185, 130 before reaching the edge. Moving lengthwise along the same fixture, they go 360, 215, 115, 60, 35 over the same distance. The light reaches roughly twice as far across the tubes as it does along them.
That is reflector geometry doing what reflector geometry does: a trough aimed down and outwards pushes light perpendicular to the tubes efficiently, and has almost nothing to work with at the ends. Every one of these fixtures behaved the same way, which means it is a property of the format rather than of any one brand.
The layout consequence is concrete. If you are running two or more fixtures over a bench, overlap them end to end — nose to tail along their length — and space them more generously side by side. Growers usually do the opposite, because side by side looks like the obvious way to fill a bench, and it leaves a dim stripe at each end of the run.
What a 6500K T5 bulb puts out
Before the footprints we also traced the spectrum of a 54 W 6500K T5 HO tube, because the number on the box tells you less than people assume.
A fluorescent tube emits through phosphors, and phosphor blends produce peaks rather than a smooth curve. What the trace shows is a genuinely broad distribution — deep blue and blue, a strong green-yellow region, and real output in the red. It is not the blue-only light that "6500K" leads people to expect.
That matters for the veg argument. Plants under 6500K T5 stay tight and short-noded because of the blue content, but there is enough in the rest of the band that the plant is not being starved of anything. If the job runs past veg, the warmer 3000K tubes shift the balance toward red and are the right lamp in the same fixture.
The T5 range today
The T5 format has narrowed a long way since this test was run. Eight-lamp bench fixtures are largely gone from the market, and what is listed now leans toward single-lamp strips, small propagation units and replacement tubes.
| Product | Format | Published specification |
|---|---|---|
| Interlux T5 Grow Bulb 4' | Replacement tube | 54 W, 4 ft, 3000K bloom or 6500K veg |
| SunBlaster NanoTech T5 HO 4 ft | 1-lamp strip with reflector | 54 W, 6400K, 3,730 lumens, 49.5 x 3.5 x 2 in, 120 V |
| Sun Blaster T5 HO Strip Light 4 ft | 1-lamp strip | 4 ft T5 HO, no reflector supplied |
| Sun Blaster T5 HO Strip Light 3 ft | 1-lamp strip | 3 ft T5 HO, for shorter benches |
| LuxStar T5 4' x 4-Bulb Fixture | 4-lamp fixture, tubes included | Four 4 ft T5 positions, takes the Interlux tubes above |
| Super Sprouter T5 HO 18 in | Propagation strip | 18 in, sized to a 10 x 20 tray |
Two notes on that table. The NanoTech reflector carries a manufacturer claim of roughly 48% more average light than the bare strip, and up to eight fixtures can be linked from one cord — useful on a long bench. And the LuxStar is the only multi-lamp fixture left on the list, which makes the Interlux tubes in the table above the practical re-lamping path for anyone still running an older 4-lamp or 8-lamp unit, since the tubes are a standard 54 W T5 HO fitting.
For a propagation bench specifically, the Super Sprouter germination kit packages a 7-inch dome and a T5 together, and the shorter 2-foot 6500K tube covers small strip fixtures. The wider propagation lighting range has the LED alternatives beside them.
Which setup for which job
The decision is less about brand than it looks, because the measured spread between fixtures is small. What changes the outcome is matching the format to the bench.
For a single tray of cuttings or seedlings, one strip fixture a few inches above the dome is the whole answer, and the 18-inch propagation unit is sized for exactly that. For a longer bench, run strips end to end along the length rather than ranked side by side, for the reason the footprints gave. For a mother plant or a small veg area where you want real intensity rather than a blanket, a multi-lamp fixture is the right shape and the 4-foot fixture range is where to start.
If the room is flowering, or if the electricity bill is the constraint rather than the up-front cost, this is where T5 hands over. A modern LED bar will put the same light on the bench for a fraction of the draw, and our comparison of LED against the older technologies lays out the trade honestly. For small enclosed spaces the small-tent LED picks cover the same footprint this test used.
Whatever is overhead, replace tubes on a schedule. Fluorescent output falls steadily long before a lamp stops striking, and lamp depreciation costs more growers more yield than fixture choice ever has.
Frequently Asked Questions
The questions that come up most often about T5 HO fluorescent lighting, answered from the measurements above.
How far above the plants should a T5 sit?
Closer than any other technology — a few inches over cuttings and seedlings is normal, and the tubes run cool enough to allow it. Our readings were taken at 24 inches, which is a bench-mapping distance rather than a growing distance; at that height a T5 is giving a small plant far less than it could.
Is 6500K or 3000K the right T5 tube?
6500K for propagation and veg, 3000K if the same fixture carries on into bloom. The spectral trace shows both are broader than their colour temperature implies, so this is a shift in balance rather than a switch between two different kinds of light.
Does the reflector really make a difference?
Between the four 8-lamp fixtures here, reflector and ballast together accounted for a 4% spread in PAR per watt — much less than the marketing suggests. On a single-lamp strip the case is stronger, because a bare tube throws half its output upward with nothing to catch it.
Can I run T5 for flowering?
You can, but the corner readings explain why few people do: under 50 µmol/m²/s at the edge of a 5 x 5 is a propagation number, not a flowering one. T5 earns its place before flower rather than during it.
Are these fixtures interchangeable on tubes?
Standard 4-foot T5 HO tubes are a common fitting, which is what made this test possible — the same lamps moved through all four fixtures. A 54 W 4-foot T5 HO tube will go into almost any 4-foot T5 HO position.
Why did all four fixtures draw different wattage?
The ballast decides how hard it drives the tubes, and these four decided differently: 393 W to 458 W on identical lamp loads. It is the single biggest reason one fixture read brighter than another, and it is the thing worth checking before paying more for a reflector claim.
The Bottom Line
Four 8-lamp T5 HO fixtures, the same tubes in all of them, and the honest result is that they are far more alike than the badging suggests. The fixture that reads brightest does so on 65 extra watts, and on PAR per watt the four of them sit inside 4% of each other.
What the data does say clearly is more useful than a winner. Check the wall draw before you compare brightness, because an 8-lamp T5 can pull anywhere from 393 to 458 watts. Overlap fixtures end to end rather than side by side, because the light travels roughly twice as far across the tubes as along them. And treat the format as a propagation and veg tool, because the corners of a 5 x 5 never saw 50 micromoles at 24 inches.
If you want a specific setup mapped, or you are re-lamping something older and are not sure what fits, leave a comment or give us a call.
This is Nate from Growers House — happy growing!