Re: I guessed you would have that explanation
TM Stock
In terms of background, Bill's usually not this aggressive in response to input, but he's still apparently a little miffed over a recent exchange I had with him on the hand tool board re: regluing failed Titebond joints. Given the sparse traffic there, I thought it worth mentioning for those here on the broader topic board that are somewhat puzzled as to the nature of the current exchange.
Back to business:
Most of the folks listening in likely have shops lit by T8 and/or T12 fixtures - 4 foot bulbs are quite common, with T8 being used in the shop light fixtures sold through Home Depot, Lowes, etc. Upgrades to newer, higher efficiency T5 to T5 HO fixtures and bulbs, as well as swapping out older magnetic and cheap electronic ballasts are certainly doable, but then we're spending enough time and money to warrant looking at life cycle cost, which is all about longevity and efficiency. Bottom line is that we're talking about 30 lumens/watt for fluorescents and about 50 lumens per watt for LEDs, with life for T8/T12 at 8,000-10,000 hours, the newest T5 bulbs at about 20,000 - 36,000 hours, and LEDs ranging from 25,000 to 50,000 hours. Last time I payed a power bill, we were still billed in kilowatt hour increments, so more watts/lumen (a lumen is a unit of luminous flux...more are brighter, etc.) means fewer bucks for the same amount of light over a given unit of time.
For new construction, I think Bill's point is valid re: new T5/T5 HO units, but again, high CRI bulbs are going to be more costly for both fluorescents and LEDs, and we will still see long term savings due to longer life and lower cost per lumen delivered to the work area with LEDs, so the trade space is defined by whether acquisition costs or life cycle costs dominate in your decision making.
Re: actual output: Why does a fluorescent bulb that generates the same lumen output end up delivering less light than an LED with the same rated output? Both bulbs are rated for total light output, but the fluorescent is unidirectional, so for the upper 180 degrees of the bulb's output to be useful, a reflector is needed. That reflector is external to the bulb - built into the fixture - and usually is no more than 80% or so efficient before internal reflection losses and degradation due to dust, etc. further reduce fixture output Mirrored reflectors are more efficient - up to 98% for practical designs - but in wood shops, those higher efficiency reflectors require some work to keep clean. LEDs use an internal mirror for each LED element, but these are sealed and suffer very little degradation over time. Further, LED output is measured AFTER losses due to less-than-perfect reflectors. So that 2500 lumen fluorescent likely delivers no more than 2250 lumens to your work space, and likely less over time as dust accumulates on the reflector. Another way to look at this is that LEDs will consume about 60%-70% as much electricity and deliver more illumination for the same rated output than comparable fluorescents.
Other considerations: both fluorescents and LEDs degree over time - both see between 5% and 15% loss in output over the rated life, with much of that near the end of their lifespan. The difference is that the current generation of T8 and T12 bulbs last about 8,000 to 10,000 hours (T5's last quite a bit longer), versus the 25,000 to 50,000 hours seen from LEDs, so florescent users will see degradation on a more frequent basis than with LEDs, but still see about the same average output.
The game-changer in all this is the newer T5 and T5 High output bulbs, which last longer, are more efficient, and - when paired with high quality electronic ballasts, can come close to the watt/lumen outputs seen in current LEDs. Cost for the technology varies, you can do the searches and see which makes sense. T5 bulbs usually are rated for 20,000-36,000 hours, so life cycle costs are not that much greater than LEDs and the HO units can squeeze out close to double the rated output (but at about double the power consumption...TNSTAAFL) per bulb. I would expect HO bulbs in LED to hit the market within a year or two, just as we now have T5 format LED bulbs.
On flicker...some people show more sensitivity than others, and older fluorescents were certainly more prone to sensible flicker than modern ballast designs. LEDs should be flicker free if driven at DC, but there are efficiency cost associated with that sort of design, so most LEDs used in the lighting we are talking about handle AC line power management on the chip, and are less likely to show some line frequency-multiple flicker. From what I can find re: trade and technical docs, LEDs are about 3 times more stable in light output than fluorescents, but unless you or someone in your shop is extremely sensitive to flicker frequency at the relatively low amplitudes seen in better florescent fixture/bulb combos and LEDs, it will likely not be an issue. My shop lighting was a mix of 20-30 year old T12 and 15 year old T8 fixtures, so certainly due for an update.