For Firefox 57, the team has been working essentially on improving CPU, GPU and memory usage, as well as concurrency. I know that some people have been looking at energy, but that's not where most efforts were spent.
I hope that our next priority becomes energy. Stay tuned :)
That's great to hear. For a lot of users, Chrome is not the competition, but rather Safari, because Safari is energy efficient and privacy conscious. If Firefox can get as energy efficient, or even just close enough to Safari then it becomes THE clear winner.
I hope that our next priority becomes energy. Stay tuned :)