I was given a bread maker a few years ago. I've used it several times, but there are disadvantages.
One is that the mixer blade in the bottom leaves a sizable hole in the end of the loaf.
Another is that the loaf is not very big. Even using the recipes for 2 pound loaves, they tend to come out more dense/heavy than large, so the loaf doesn't go as far as commercial bread.
On the plus side, however:
The taste, on the other hand, is far superior, and you KNOW what has gone into your bread...(nothing you can't pronounce)! But then, that's true of any homemade goods....
It IS faster than making bread by hand--the knead/wait/punch down/knead/wait, then bake times are very much shorter, so you have your loaf in 2 or 3 hours, instead of half the day.
As far as whether it saves energy, I'd imagine it takes less electricity than firing up the full-sized oven, but if you have a gas oven, I don't know how to make that comparison.