I have the 2015 rMBP 15" basic model. I constantly have activity monitor showing CPU in the dock to see if CPU consumption is increasing for some reason. You

I have the 2015 rMBP 15" basic model. I constantly have activity monitor showing CPU in the dock to see if CPU consumption is increasing for some reason. You can check the activity monitor CPU tab and the Energy tab for energy consumption issues. There are also 3rd party battery monitors (e.g., Coconut) which will tell you the up-to-date energy consumption.