Macbook Pro battery life with Android Studio 2.2 running
There was a long-standing problem with Oracle JDKs/JREs causing the discrete video card rather than the integrated one to be used on Retina displays, with a consequent hit on battery life. The problem became apparent when JetBrains started bundling Oracle's JRE with IntelliJ-based IDEs (see, for instance, IDEA-119858 in their bugtracker). Android Studio is based on the IntelliJ platform so would have suffered from the same problem.

That said, the problem has been fixed for quite some time in JetBrains IDEs like IntelliJ IDEA, and issue 80173 in the Android Studio tracker says it was fixed in Android Studio 2.2. So since you say you're using the latest version perhaps your problem has another cause, or perhaps the problem's not in fact fixed in all cases. gfxCardStatus (as linked from the JetBrains bug report) might be useful in checking which card is actually being used. I used the tool for a while on my own mid-2012 Retina MacBook Pro back in the days when IntelliJ IDEA was suffering from this problem.