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Is there a way to calculate how much brighter a T-5 is than a comparable T-8?

For example, a 22" 14 W T-5 vs. a 24" 20W T-8?


I ask because I am curious if a double strip with two T-5s might actually be too bright for plants mounted up near the strip (not Neos, of course :)

Thanks.
 

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that will not be to much, unless you have a fancy reflector for the bulb it will have a tiny bit less light.
 

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I haven't really looked into short lengths like that, but at 48", they have very similar light output, with a slight advantage to the T8. (t5 more efficient, t8 more watts). Once you put individual reflectors on the T5s though, they're MUCH brighter than the T8s.
 

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Another thing to keep in mind is that there are a couple different T5s. Regular and High Output. Efficiencies, in lumens per watt, for the typical 4ft bulbs are 104 for T5, 93 for T5HO, and 96 for T8. I've seen different numbers stated on different websites, but these are good enough for a comparison.

Taking these efficiences and multiplying by there respective wattages per bulb, you can get the total lumens per bulb.

So...

T5: 104 lumens per watt, times 28 watts per bulb, equals 2912 lumens per bulb
T8: 96 lumens per watt, times 32 watts per bulb, equals 3072 lumens per bulb
T5HO: 93 lumens per watt, times 54 watts per bulb, equals 5022 lumens per bulb

Regular T5s and T8s are very close. Currently, T8s are cheaper, due to their wider acceptance in the commercial lighting business.

But that's changing, T5s are coming on strong and the prices are dropping.

T5HO provide considerably more light, as you would expect given their higher wattage.

T5HO bulbs and fixtures are more expensive.
 

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T5: 104 lumens per watt, times 28 watts per bulb, equals 2912 lumens per bulb
T8: 96 lumens per watt, times 32 watts per bulb, equals 3072 lumens per bulb
T5HO: 93 lumens per watt, times 54 watts per bulb, equals 5022 lumens per bulb
Just as a note, these numbers are only valid at 48" bulb lengths, and there are "super-t8" bulbs that are up at just over 100 lumens per watt.

96" bulbs (across all 3 technologies) are slightly more efficient. As bulbs get shorter, they get less efficient. The 14w 24" T5s are less than 90 lumens/watt.


The two real advantages of T5 are this:

1) Reflectors. The slimmer design makes it much easier to design an efficient reflector. T5 parabolic reflectors are about 2" wide. To do the same thing for a T8, we're talking 4-5" and 6-8" for a T12.

2) Ballasts. The vast majority of T8 ballasts out there are magnetic, and a large percentage of the electronic are really old designs. Good T8 Ballasts are similar to good T5 ballasts, but there are very few bad T5 ballasts commercially available. As T5s move into $<25 shoplights, this will likely change.
 
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