I have more energy too when I am on Prozac. I used to be very, very tired and had no energy at all---for a long time I really thought I was sick because I was so tired all the time. But once I started Prozac, I could go out more.
It does make me sleepy sometimes, and I even fell asleep at my desk at work a few times.
However, this sleepiness is very different from and much better than the tiredness I had before. Now I can sleep whenever I want, but when I wake up I feel more energetic. I know it sounds strange, but this is the way Prozac makes me feel. I feel more relaxed when I am awake, and when I want to sleep I never have a problem doing so.