On a previous laptop, the performance/powersave mode under 16.04 worked exceedingly well. I had an ASUS RoG 17.3" with two HDD and GTX 860m running at 9-11w while running office applications. This meant about a 5.5-7hr battery life on a gaming laptop! (I of course used TLP). It would outlast my classmates' macbooks and tablets. On performance mode, consumption would run 25-40w.
Currently, I have found some strange things happen under the Xserver since 18.04 and a new laptop. For instance, as indicated by Powertop, when Xserver is set to powersave mode, usage is about 29-31w at idle--very high for my 15.4". When set to performance mode, usage is generally 19-22w, which is somewhat marginal, but lower!
I have a hunch the gpu is not disabled under powersave mode and it is running at unwarranted stress levels, as my fans are kicked up but CPU is still running at low 800-805 MHz as shown by grep, and managed by TLP.
Though my current setup is a GTX1070, the above problems do not make sense to me since powersave causes massive power consumption. I am also reluctant to attempt Bumblebee, as many have indicated it is currently shady with 18.04. Is there a simple but reliable way to force Intel HD and disable the GPU? I use this for work and games, so I don't want to risk breaking the install by driver-switching frequently.