I used a Kill-a-Watt Devices and Tested all my components in all modes.

After reading all kinds of posts and insufficient details from Sonos, I have the final word calculated.  Enjoy : )

CONCLUSIONS:
Leave them all on and do as you wish.
It would cost me $84 to run my entire system Low Volume 24/7 for a Year.
It would cost me $33 to have my entire system Plugged-In Ungrouped Not-Playing for a Year.
Hence, selectively stopping, muting, or ungrouping as I "Change Rooms" is a waste of time.
UnGrouping is slightly more efficient than Mute.

The powerful Play 5 is the largest energy draw, roughly double the other units, at $14 per Year 24/7 Low Volume.
The Play 1 is the smallest energy draw, roughly half the average of the other units, at $4.43 per Year 24/7 Low Volume.

Spreadsheet with all figures and data for your use.

Enjoy - Walt