I plugged my One SL into a measuring device and see it seat at 3.9 watts when idle, which is a bit more than this support document advertises (3.4 watts). I have a pair so that’s about 8 watts, running 24/7 that makes about 6 kwh/month. It seems kind of wasteful to me for devices just sitting there doing nothing. Apple’s HomePod has a low power mode that make it run at 1.76 watts when idle. Surely Sonos can do better.
I honestly wouldn’t mind if my device takes a bit longer to start when I get back to it. It’s not doing anything most of the time so saving power would seem to make the most sense. Hopefully Sonos can deliver something in a device update, even if it is an opt-in low power mode, I would gladly enable it.