According to the energy calculator I just checked, it costs in rough terms, $1/month to run a 60 watt bulb 5 hours a day.
An LED bulb would use 1/6th of that, or 10 watts. A savings of .90/month
If I had 5 bulbs, running 5 hours a day, or an average of 50 hours of combined use of lighting in a day, I could save roughly $2.25 a month.
My bill averages about $185/month, so $2.25 would be a 1.25% difference.
The price of LED bulbs has come down, making the investment needed to do do that, more worthwhile.
But, the actual life span of the replacement bulbs, in my experience, has been disappointing, making it less attractive.
Almost all of my lights are on dimmers, (even the outdoor ones), and kept dimmed most of the time. Some LED's can't be dimmed. And, most LED bulbs, do not warm in color, like an incandescent does, as they dim. Which is something that I prefer. I would rather not give up, to save a couple of bucks a month.
"Warm on dim" LED bulbs are being offered now, but they are of course, even more expensive. Those are far superior to those which don't warm at all, but when I tested them, still not quite the same. So, the majority of my light bulbs are still incandescent.