T8 Fluorescent LED Replacment Bulb Energy Consumption

[semipro]

I thought I'd give some of these LED bulbs a try in a fluorescent shop fixture.
http://www.homedepot.com/p/Philips-4-ft-T8-17-Watt-Daylight-Linear-LED-Light-Bulb-456608/206278132
Observations:

• Energy consumption measured using a Kill-a-Watt:
  • Dual bulb, electronic ballast, fixture only: ~5 watts
  • Fixture with two 32 watt (rated) fluorescent bulbs: ~48 watts
  • Fixture with two 32 watt equivalent LED bulbs ~ 39 watts (~23% decrease)

• Anecdotally
  • The LEDs came on instantly in my cool garage (probably 50 degrees F)
  • The light output seemed higher (but the existing bulbs are a few years old)
  • No discernible audible noise but I don't hear higher frequencies

At $0.12/kw-hr the break-even point is about a year's full-time usage in a bulb rated to last 4 years. (time value of money not considered)
I plan to install 4 more in the kitchen today in a fixture that gets heavy use.

Edit: The 4 I installed in the kitchen seemed to have really brightened the place though its hard to be objective since I went with a 5000k replacement and am sure the former bulbs were of a lower color temp.

 

[DBoon]

How do you like the light quality from these bulbs? Is there a CRI rating on the packaging?

 

[semipro]

How do you like the light quality from these bulbs? Is there a CRI rating on the packaging?

Seems okay to me but I'm I don't seem to be that sensitive to the color temp or spectra.
This document would seem to indicate a CRI of 82. I see no CRI rating on the box.
http://images.philips.com/is/conten...07_001-UPD-en_US-PLt-1309BN-LED-T8-IF-Web.pdf

 

[DBoon]

CRI of 82 is pretty reasonable for this...

 

[williaty]

CRI of 82 is pretty much the minimum acceptable for non-color-critical tasks. Hallway lighting, closet lighting, etc. Wouldn't cut it for kitchen (need to see colors correctly for food safety), the bathroom (women doing makup, checking clothes), or a hobby room with stuff involving colors.

That being said, the thing you really need to compare is the lumens per Watt, not just the Watts consumed by the fixure. T8s range from 83 to 100 lumens per Watt, with the average tube being right around 92 lumens per Watt. You've got to compare that to LEDs you're considering using. LEDs cover about 60 to 110 lumens per Watt, so you can see that you have to pick your LEDs carefully to end up with something that's any better than a T8. Often, when you see an LED replacement pulling less power than a T8 (or T5), the reason isn't that it's more efficient, it's that it's making less light. Your eyes are pretty terrible about noticing this as well because they get so confused by other changes in the look of the light due to the swap. Where linear fluorescents may fall short compared to LED is the aging process. The T8s typically have about a year's worth of 8-hour days in them before they dim significantly. When they age out, they make less light but don't consume any less power. So you might find that in the 13th month, the LEDs are considerably more efficient because they haven't dimmed nearly as much due to aging. Cost comparisons of linear fluorescent to LED replacement should factor in yearly re-lamping of the linear fixture.

 

[FTG-05]

The two LED bulbs are 34 watts total, not 39 (17 watts each).

The bigger point is the 123 lumens per watt; that's a pretty good ratio of light to power.

I like the LED florescent replacement bulbs that bypass the ballast, no loss in the ballast.

 

[semipro]

I like the LED florescent replacement bulbs that bypass the ballast, no loss in the ballast.

I'd like that too. Do you have a link?

 

[williaty]

The two LED bulbs are 34 watts total, not 39 (17 watts each).

The bigger point is the 123 lumens per watt; that's a pretty good ratio of light to power.

I like the LED florescent replacement bulbs that bypass the ballast, no loss in the ballast.

123lm/W is a VERY good efficiency. However, whenever LED manufacturers claim something that good, I immediately get suspicious and look at color temp and CRI. Looking at the OP's link, it's for 5500K and 80CRI. So too blue and not quite good enough CRI for anything. Efficiency tends to go down if you go to a warmer color and better CRI Actually, it's interesting that there's different claimed CRIs for what's being sold at HD vs what the OP found in that PDF from Phillips.

I'd be very, very excited to see a >120lm/W efficiency on something at 4100K and >85CRI. I'd be ESTATIC to see >100lm/W in something 3000-3500K and >90CRI because then we'd finally have something to replace the discontinued Philips L-Prize lamp.

 

[iamlucky13]

So too blue and not quite good enough CRI for anything.

80 CRI is fine for most purposes, with some caveats related to how the CRI test actually works. Most people never notice the difference between an 80 CRI LED lamp and any of the significantly higher CRI lamps.

I've tested different lamps with my camera to see what the differences are. Freezing the lighting in a photo allows you to compare differences more obviously than judging based on memory, especially since our brains do such an effective job of normalizing what we perceive in different lighting conditions.

What I see is that deep reds and deep purples under 80 CRI LED's tend to look subdued, dull, or slightly shifted to orange or blue respectively, compared to incandescents.

Fluorescents usually have a bit of extra green and magenta compared to an ideal emitter at the same color temperature. After correcting the color balance for this, there's still a few scattered holes in the spectrum where they don't illuminate certain colors well. I've particularly noticed this in the green-yellow range on certain foliage and one of the green paint colors we use in our house, which looks dull and almost grey under fluorescent lighting, but is a nice earthy tone under LED or incandescent lights. You can see why if you look at the spectrum of such bulbs like this:

https://astronomylog.files.wordpress.com/2011/11/cfl-spectra.jpg

All things considered, the two places where I care enough to seek out high CRI bulbs is the kitchen, where I'm looking closely at food that might not look as appealing under bad light, and the bathroom, where we're likely to pay close attention to skin tones in the mirror, which we naturally perceive subtle differences in well.

Pretty much anywhere else, I'll stick with the less expensive, more efficient ~80 CRI bulbs.

Even then, that's partially just because I'm obsessive about such details. My wife thinks I'm silly in being picky about it.

 

[williaty]

80 CRI is fine for most purposes, with some caveats related to how the CRI test actually works. Most people never notice the difference between an 80 CRI LED lamp and any of the significantly higher CRI lamps.

My experience having done theatrical lighting, photography, and photographic printing professionally is somewhat different to yours. If you ask people a question they have no context for such as "which of these has a better CRI?", they'd be lucky to tell a 100CRI light source from a 20 CRI light source. Ask them "which one makes the colors prettier?" and they can tell a 90CRI from a 70CRI. Ask them "Which light makes Aunt Edna look better" and they can tell an 80CRI from an 85CRI light source. A big part of this whole transition is that people have no experience and no context for lighting choices because they've had only 100CRI 2700K incandescent lamps to look at until the last 10 years. This is why CFLs had such a rough go. Because people had no experience looking critically at light, they didn't notice what terrible lights they were. However, they did notice, after a couple of weeks, that everything looked terrible, their eyes hurt, Aunt Edna looked sicker than she used to, and sometimes when you went outside into the sun you found your clothes didn't match like you thought they did.

People's unconscious relative colormetric precision is actually pretty good. Their understanding how how to articulate that and how to deliberately perceive that is pretty bad.

 

[begreen]

Ain't nuttin gonna make Aunt Edna look better but some new teeth.

 

[iamlucky13]

williaty - I agree that you can usually tell if asked to in a side-by-side comparison.

However, "Look at subjects under these two lights and tell me what looks better" is not a common decision criteria. Screw the bulb in and see if your room looks good enough that you'll buy more is.

That test tells us that most people dislike CFL's, but find 80 CRI LED's acceptable. I'm guessing that's more because of the typical green-magenta hue of CFL's than their deep spectral gaps, although I also think the depth of those gaps is a bigger liability than the wider, shallower gaps of LED's. Despite being one of the very few people who have ever set up a side-by-side comparison of several bulb types, I'm one of the many who's content with 80 CRI LED's (again, except in the bathroom and kitchen).

This is borne out both in user-reviews and in sales. The 80 CRI bulbs are flying off the shelves. The 90+ CRI bulbs are selling so poorly (albeit, mostly because of price) that Home Depot has pulled them from the shelves in most of their stores.

So I stand by my argument that 80 CRI bulbs are fine for most uses.

 

[williaty]

I'm 100% sure the reason the Cree TW lamps haven't sold well is the price premium compared to the normal series lamps coupled with the complete and utter lack of any information as to why they're better. That's ESPECIALLY true here where AEP (local power company) is subsidizing the cost of the normal Crees to under $2 for the 60W. I've been at HD on at least 4 occasions now where I was shopping for some odd lamp and heard another couple trying to make a decision about a 60W A19 replacement. Every time, I heard them say, to paraphrase "It costs more, it isn't brighter, and it uses more electricity. What's the point?". Every time I've stepped in and explained CRI, the couple have done what you'd expect and bought 85 CRI Crees for most of the house and TW Crees for the kitchen, bathroom, and whatever space she picks out clothing in.

HD could dramatically increase sales of a higher-cost item if they just educated their staff so that they could explain this to customers, but that would mean the end of the world!

 

[Seasoned Oak]

Iv been buying LED shop lights at sams for $36. THe lights are built into the frame and made to look like regular shoplights but are not seperate Bulbs per se. They seem to throw more light than my recently purchased T-8 shoplight fixtures and bulbs that also go thru bulbs rather quickly.
They have dozens of small LED lights running the length of the fixture and come on instantly. NO going back to old tech for me. Uses 40 watts total.
(broken link removed)

 

[maple1]

I'd like that too. Do you have a link?

Search Ebay for 'LED tube'. There is a pile of stuff on there that nobody around my parts has even heard of yet. Quality is always questionable on stuff thru Ebay from the Far East, IMO, but seems tech is very slow to make it to my neck of the woods so some experimentation may be warranted.

 

[jebatty]

I bought a 10-pack of these from HD for $89.97 + sales tax and free shipping, arrived yesterday: Philip, Model # 456590, Internet # 20640286, 4 ft. T8 17-Watt Cool White Linear LED Light Bulb (10-Pack). Box description also showed: 2100L, 4000K, CRI not shown.

They replaced 10 florescent T8, 2800L, 32W, 4100K, 75 CRI tubes which had light to moderate use for 5 years. The new LEDs were instant on brightness and to my eyes appeared noticeably brighter than the florescents they replaced. The CRI was not stated for the LEDs. Other Phillips LEDs have CRI 82.

 

[maple1]

Did they keep the standard ballast & starter in place?

Most of the ones I looked at on Ebay called for the removal of ballast & starter - which seems to me to be a good thing.

 

[semipro]

HD carries both LED replacement types: the ones that require fixture rewiring and the ones that don't.
The former were $30 apiece, the latter $10 apiece.
To my original post, the new LED bulbs are definitely brighter than the T-8s they replaced. One of my sons who was not around when I replaced the bulbs noticed how much brighter the kitchen was when he came home.

 

[jebatty]

Mine used the existing electronic ballasts in the fixtures.

 

[iamlucky13]

As I understand it, the ballast will still draw some power. I'd be curious if the "instant fit" type LED's can also run straight from 110VAC if a user decided to remove the ballast, or if they require it to remain in place.

Very interesting that even somebody who didn't know the lights were replaced attested that the 2100 lumen bulbs are brighter than the 2800 lumen bulbs.

 

[semipro]

Very interesting that even somebody who didn't know the lights were replaced attested that the 2100 lumen bulbs are brighter than the 2800 lumen bulbs.

My thought too. How human perceive light (and perhaps process the related imagery) is interesting and complicated.
The bulbs I installed were of a higher color temp so that may explain a lot.

 

[jebatty]

There is another reason a lower lumen output from a LED may be brighter than a higher lumen output from a T8, and that is the LED projects all of its light at a downward angle, no light is projected upward, so all the light goes to the surface being lighted, and especially not to the ceiling or the reflector above the tube. It may be that a lot of T8 light goes where light isn't needed, that is, wasted lumens.

 

[seige101]

Also something to consider is lumen depreciation from the old T8 lamps. Brand new out of the box they will give you 2800 lumens. They will get less and less brighter until end of lamp life.



Almost always people don't replace the lamp until it burns out

 

[begreen]

I've had 2 outright fail to start T8 bulbs in the past few years. One bulb was brand new and the other only had maybe a dozen hours on it. If the LED tubes work better I may get some too.

 

[BrotherBart]

I need get a couple of'em for our kitchen. The two in that fixture are wearing out our electric meter.