Currently running Elementary Luna on my laptop with switchable graphic cards. Laptop some time goes hot near the touch pad area with fan noise and hotness. Did a bit research and find out that it was ATI card ON by default. Battery usage was 1 to 1.30 hours on ATI by default. I have ATI 6600M with Intel integrated graphic card. From my previous openSUSE experiments, tried some solutions and can say things are much better now with Intel card[switched]. Battery life goes from 1/1.30 to 4/5 hours dramatically, no more heat issue and noise. Temperature dropped to around 50C for CPU and around 47C for HDD, which i still think is a bit high(working on it). So here is what i did.
Just for monitoring purpose, install lm-sensors and hddtemp. Sudo apt-get install in terminal will do it.
Now edit the following file with sudo(assumed terminal is open):
sudo vim /etc/rc.local
Add the following lines before exit 0.
chown -R $USER:$USER /sys/kernel/debug
echo OFF > /sys/kernel/debug/vgaswitchero
Reboot, and see if that helps. You can view in terminal which graphic card is active now:
sudo cat /sys/kernel/debug/vgaswitcheroo/switch
IGD = Intel
DIS = ATI [Discrete]
Even can switch back to ATI [need to logout and login for this to take affect, discrete card will be active(ATI)](not tested):
echo DIS > /sys/kernel/debug/vgaswitcheroo/switch
To turn OFF the in-active card:
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
I will do more research on this to minimize the heat. Will share my findings here. Stay tune.