My shop is lit by 4 ft x 2 tube fluorescent lights. They have 32 watt lamps (T8) with new blasts in 2011. In 2016 I replaced one fixture with a 4 ft LED from Lowes. There may be some loss of brightness in both types over time but since these are all at least a year old they are reasonable representations of what I can expect. (my shop time is about 16 hours/week) The LED is as close to exactly the same light output as the fluorescents as I can judge by eye.
Am I saving enough power to make it worth replacing the other 6 fixtures? Based on literature, sales and scientific, the answers range from "no savings because fluorescent is good also" to "these lights will cut your electricity bill in half"
This week I got a Kill-a-watt power meter.
51 watts flourescent
37 watts LED
14 watts x 16 hours/week x 52 weeks/year x .1717$/kwh = $2 per year per fixture.
This is not a big savings, however since the fluorescent tubes burn out pretty often, I may do it.