Using nouveau doesn't imply the card will always be on. Assuming the firmware on the device turns it off and on, vga-switcheroo or bbswitch will send the proper ACPI commands to turn it off and on. When it is on the chosen driver will be used.

On Tue, Dec 16, 2014 at 5:46 PM, Erik Mackdanz <erikmack@gmail.com> wrote:
Heiko Baums <lists@baums-on-web.de> writes:

> I don't know if, but I don't think that, it will work with
> x11-drivers/xf86-video-nouveau.

I used bumblebee for quite a while.  It worked okay, but every upgrade I
would have to fiddle with it again.

I switched to the Nouveau driver and I'm very glad I did.  "Conventional
wisdom" says Nouveau quality is lower than Nvidia, but I found it worked
better on some things (Second Life).

As someone else pointed out, with Nouveau the GPU remains on all the
time consuming power.  This is the downside.

If ease-of-use and/or open licensing are more important to you than top
rendering quality and power consumption, consider using Nouveau.

--
Erik Mackdanz