"Pretty cheap" is still likely an order of magnitude or more than actual standby, and using a small ring buffer to identify a pre-established wake word is simil

"Pretty cheap" is still likely an order of magnitude or more than actual standby, and using a small ring buffer to identify a pre-established wake word is similarly going to be cheap compared to actually streaming audio to disk. If you actually care, this would be pretty trivial to verify using an oscilloscope to observe the energy draw from the battery while different things are said around your device.