I find its all WiFi. On an xps 13 with ubuntu, I get 10-12 hours on low brightness without wifi, but often 4-6 otherwise with wifi. Its really nice for roadtrips.
I wonder whether that is causation or correlation?
AFAIK the WiFi hardware doesn't use much power itself, although I might guess that background protocol chitchat could cause CPU usage. I think that when I am usually using WiFi I am also usually using a browser that chews power.
This is my thought. Turn off wifi and you're no longer running the cpu and memory monster that is a web browser.
But this is something Apple does right. My wife noticed that she can get around 50% more battery life out of her Macbook using Safari instead of Firefox. (7-8 hours instead of 4-5).
AFAIK the WiFi hardware doesn't use much power itself, although I might guess that background protocol chitchat could cause CPU usage. I think that when I am usually using WiFi I am also usually using a browser that chews power.