I was in a Northern Tools retail outlet looking for something and didn't find it, so as not to waste the visit asked the manager about what was new. He recommended LED lighting. They had a combination of LED high hat and flurescent and I couldn't tell the difference from the ground. Same color and light output.
I didn't want high hats, but was interested in replacing linear 32 and 40 watt four-foot lamps run by magnetic or newer electronic ballasts. Northern was selling a 17 watt direct drop-in replacement for those for $20 a pair (at 5000K).
I bought a pair and swapped them out in a fixture at church that used 32 watt T8 tubes. No rewiring, just swap out the tubes. Brighter than the 32 watt tubes, too.
Only problem is the price. $10 a tube would take a long time to pay back when electricity here is cheap (10 cents a KWH). If a tube saved 15 watts is 1.2 cents a day at 8 hours a day on. A 32-watt tube is about $3 a tube in a bulk pack. That means the LEDs would take about a year and 8 months to break even.
The real energy saving are not as advertised, either. I plugged in a pair of LEDs into a new electronic ballast and my Kill-A-Watt meter said the 32's used 30 watts and the LEDs used 20 watts.
That makes the pay back just under 2 1/2 years.
Amazon advertised the same type of lamp for $6 each, a much better deal, but the reviews were mostly bad, saying that the LED dropin tubes were picky about the ballasts. I do not have an Amazon account and didn't want to buy tubes like that by internet.
I shop Walmart 5 days a week to buy food for the day before going off to work. This particular WallyWorld has a tire shop and full tool and hardware selection and they also sold 2 packs of dropin LED tubes for $4.90 a tube. That was cheap enough to gamble on and they worked well, except in a fixture I knew was dying and had to be replaced anyway.
Walmart sold boxes of 10 for $43, so I went around buying up their local stock. One manager told me the tubes were "no replenish" but he didn't know why they were being discontinued. I have bought 7 boxes of 10 so far and won't need more for a while, as I am only doing special replacements. The older 40 watt tubes are so dull that 2 "20-watt" LED tubes provides as much light as four 40's saving 120 watts a fixture where we were still using the 40 watt tubes.
I prefer the direct dropin replacement because it does not mean making any wiring changes. I cannot trust that someone will not come along behind me and put a regular tube back in. That might create a hazard if I had to disconnect ballasts or cut the wires on one in, which are the other two options other than complete fixture replacement.