My son just bought a set of the currently available LEDs and although they are a bit pricey, they last darn near forever....and they are programmable (the really fun part).
We bought the LED lights for the indoor trees (2 huge ones!), and will be watching for them to go on sale after Christmas for the 50 ft tree outside.
Did we do it because we care about global warming? Hell no, it’s 17 degrees out! We can only hope all those lights warm it up! We did it because they’ll lower our massive Christmas season electric bill.
Gotta be careful which ones you choose, however. We’ve found that the closer together the bulbs are, the cheerier and brighter they are. I found this out the hard way, after the upstairs tree was all decorated, including the individually placed icicles. Ever try taking the lights off (and then replacing them) a tree without disturbing the ornaments or icicles?