The short version:
Your laptop's HDMI port is wirred to the nVidia card in Hardware. No software solution can change this, you need to resort to a mini-DP --> HDMI hardware convertor to make this work.
From: Aero 15X v8 annoyances:
Second issue has to do with Nvidia optimus and essentially requires me
to relog or restart the pc when I disconnect from an external display
to keep the battery from draining running on the gtx 1070. Assuming I
boot the PC without any external displays connected, non-game
applications will utilize the onboard gpu as expected. If I boot the
PC with an external display connected however, everything (web
browsers, even windows shell) will use the dedicated gtx 1070. This
also applies to any applications started when connecting an external
monitor after booting. None of the applications will switch to the
integrated gpu after disconnecting the monitor and nothing short of a
relog/restart will solve the issue.
I've tried forcing global settings in Nvidia control panel to the
integrated gpu, updated all drivers but all to no avail.
Any advice would be greatly appreciated.
In the answers section this is discovered:
This is not the case with the Aero 15 however. It seems that the
display outputs are wired to the GTX 1070 which forces all
applications that were started on any display connected to the
HDMI/mDP port to be rendered with the GTX 1070.
I tested this by having the laptop's screen enabled while connected
via mDP to an external monitor. If the built-in screen is set as
primary, applications launched will run on the iGPU. When the external
monitor is set as primary, all applications started will run on the
Note: My Alienware AW17R3 has the external HDMI port hardwired to the nVidia Geforce GTX970M GPU as well and I cannot use the Intel iGPU to drive the Laptops HDMI external port. The Intel iGPU will only drive the builtin display and Thunderbolt 3 USB-C port which has a DPI-->HDMI adapter ($25) to another external monitor.