Originally I had terrible battery performance like what you are describing. I have a dell xps 15 9560 with a 97Wh battery. With bumblebee installed with proprietary nvidia gpu drivers I can get all day battery life no problem (easily 10+ hours of active usage). The same cannot be said for when its booted into the windows partition. Yes this is because of the gpu settings but why would windows need to utilize it with everyday tasks like google docs or casually browsing the web? It took some work to get the battery under control but after I did some reading about drivers and bumblebee I didn't have any problems. Been on this install for a bit over a year now without any show stopping issues.