added kernel option i915.i915_enable_rc6=1 & i915.i915_enable_fbc=1

Makefile

@@ -0,0 +1,2 @@
+fetch :
+	cp /etc/default/grub ./grub 

grub

@@ -4,7 +4,8 @@
 #   info -f grub -n 'Simple configuration'
 
 GRUB_CMDLINE_LINUX=""
-GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux nmi_watchdog=0"
+# https://ivanvojtko.blogspot.co.at/2016/04/how-to-get-longer-battery-life-on-linux.html
+GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux nmi_watchdog=0 i915.i915_enable_rc6=1 i915.i915_enable_fbc=1"
 GRUB_DEFAULT=0
 GRUB_DISTRIBUTOR="Fabian Peter Hammerle <fabian@hammerle.me>"
 GRUB_HIDDEN_TIMEOUT=0