Why Always-On Listening Costs Battery
Continuously running even a lightweight wake word model draws meaningfully more standby power than a push-to-talk design, since the microphone and detection chip never fully sleep.
Design Choices That Help
Low-power dedicated wake word chips (rather than running detection on the main processor) and adjustable sensitivity/duty-cycle settings both help manage this trade-off — worth discussing explicitly with your manufacturer if battery life is a primary marketing claim.