I just replaced almost all the light bulbs with LED in my new apartment.
I first pulled two 100W bulbs that were installed in 40W max fixtures (!) -- not counting two more that were burned out. All four were blackened on top.
Then I replaced a 60 W bulb. The previous tenants had put two 26 W CFL bulbs in a closet fixture. I'm not sure why they needed quite so much light in that closet, so I moved one.
So that's 260 W removed.
Then, flying home from a business trip, I brought two 6-packs of 2700 K, 800-lumen, 8.5 W bulbs from Phillips. They were $13 each six-pack. Also, while I was away my partner unpacked an old spare bulb I'd packed with some of our books: 3000 K, 800-lumen, 10.5 W. Just a couple years old, but even that small amount of time saw a 20% improvement in efficiency.
I found exactly 13 bulbs to replace. 8x 60W, 5x 40W, a total of 680 W.
So that's 940 W replaced by 112.5 W, my closet is slightly less bright, other rooms are equally bright, and my apartment slightly less likely to catch on fire.
Now the lights aren't always on. The usual estimate is that lights are on for 3h a day. So that's about 100W saved on average, year-round. Or about 3-4 cents per hour at the utility rate here.
I'm not sure what to do with all that money.