In case of alternator failure

In an attempt to pre-plan such an event as an alternator failure, I wanted to discuss electrical load shedding with an IFD540 installed.  I also have a KX155 navcom and of course a handheld.

How does the IFD 540 compare with a dedicated transceiver such as the KX155?  I could use the iPad for navigation in an emergency so really don't need the GPS.  If I needed the RNAV approach capability, I could cycle it on later. Does booting up the IFD use a lot of power going through its checks, is it better to just leave it on?  Are there features within the IFD 540 that can be turned off to preserve power in any meaningful manner (for example does it save that much by turning the brightness way down)?  I also have the AXP340 transponder, which I would turn off in cooperation with ATC.  Perhaps you could comment on the AXP 340 as well.

Hopefully you can get the gist of my question. I realize it's kind of an open-ended question but don't want to go down the rabbit hole of dual alternators etc, just wanted to keep it a discussion of what alternatives do I have to cope with an electrical failure.

Thanks