I use a Macbook Pro (2014) with Kubuntu Linux installed full-time. The battery life is about half of what it is when running OSX.

If you forget your charger, there is serious range anxiety. Luckily, I've been running PC laptops for years and have gotten completely used to bringing my charger any time I take my laptop.

I get ~3/4s of the battery life that i have on osx if i do not run anything on flash.

if flash starts, i get less than half. (using archlinux on a mid-2012 mbp)

I estimate that I get better than half of the battery life.

Years ago, when I started doing it, the battery life of Linux on Macbook was really terrible.

I only need a couple of hours of battery life for my mac at most, so that's fine for me at least.