OP-->As said above.+1
OP>> Battery life is going to be all over the place on the Yosemite beta. Just erase it and go back to Mavericks if you want good battery life.
You can´t expect to get quoted battery life when using beta software.
When i tried out the public beta i got between 4-5 hours of battery life with no cpu intensive tasks(safari, pages and numbers) before it was drained.