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When inserting a LED tube light into the fixture, do I need to orient the tube in a particular direction? Or would it output light in all directions?

I am about to replace my existing fluorescent T8 tube lights with LED ones. I see that GE's T8 48inch fluorescent lights output about 2900 lumens (example). On the other hand "equivalent" LED ones output only 1800 lumens (example). On an unrelated website called WaveformLighting, I see an article that fluorescent light waste almost half of their lumens because they emit light in all directions. So a LED tube light with about half the lumen will do fine, assuming it's directional. The lights sold on WaveformLighting do have directional lights. enter image description here

However, when looking at the picture of GE light, I don't see any such thing - it looks almost the same as a fluorescent light - emitting light in all directions (sorry for the bad quality image, this is the best I could find on lowe's). enter image description here

None of the description, specification, pictures or installation video mention anything about orientation.

So, does the GE light emit light in all directions? If so, then should I be looking at a higher output LED tube light to get the same effective brightness as the fluorescent ones? Because otherwise I can't fathom how a 1800 lumen light is equivalent to 2900 lumen light.

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  • Another possibility is that the 2900 lumens is the peak output and that the average output is 1800. I.e. fluorescent lights flicker, not always producing the same level of light. And of course, we don't know if GE considers their LED lights equivalent to their fluorescent lights. It's equally possible that they think that their fluorescents are better than normal and their LEDs are equivalent to normal.
    – mdfst13
    Commented Jul 22 at 12:58

3 Answers 3

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Any comparison can only hold for a certain fixture.

For the highly reflective, carefully shaped, fixtures in work, you can assume that (nearly all of) any light emitted upwards ends up in the room. For the ones I have at home, any light emitted upwards hits white-painted metal, and most of the light reflected from that ends up going back to the source (worse, some hits the ceiling). In the latter case, the lower output may be sufficient below the lights, but in a big room you may have a bit more contrast between light and dark regions than with omnidirectional emitters.

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  • Thanks. It does sound like it will depend heavily on the fixture. My fixture is also white painted metal, so some light will get wasted. I think I can try out the GE lights and observe. There is only so much information I can get sitting in front of the computer :)
    – Turbo
    Commented Jul 23 at 6:13
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The LED bulbs with half or double the lumens are not intended to compensate for directionality. That rarely matters, especially in residential ceiling fixtures. The different brightnesses simply allow you to provide more light or less light in the same size fixture, according to what you want.

Fluorescent tube light output is correlated with length. LED replacement is more flexible. For a given length they can use different kinds of LEDs and multiple rows of them to make bulbs with different brightnesses in the same length. So you get to choose and don't need to worry too much about comparing with the old bulb. Get what you want.

Fluorescent ones do shine in all directions but are often installed in fixtures that direct all the light down. An LED replacement shines only down. This usually won't matter. This matters if the fixture:

  • is highly mirrored and lensless. Then the LED replacement may spoil the design of the fixture
  • is very open and designed to light up the ceiling and walls above it at least to some extent. The LED replacement will not do that as well.
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Someone asked a similar question on Lowe's product page for this. Pasting the answer below.

Q: Brightness between GE 6500k fluorescent and direct wire 6500K LED 4 ft tube. Why is fluorescent showing 2900 lumens and LED showing only 1800 lumens?

A: The fluorescent tubes give light in all directions, so about half the light is lost shining upwards into the fixture. The LED tubes give light only downwards, so they are more efficient in delivering light. GE Lighting, a Savant company

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