Recommended · for some experience
Extreme Power-Save Mode: ESP8266 powered ON after External Interrupt
Why people recommend it
Shows an ESP8266 kept fully off through its CH_PD pin and powered up by an external interrupt; suggested for battery sensors that should only wake on an event.
In their words
Just stumbled upon this video, using of CH_PD pin to turn the chip completely off.
Maple on electronics.stackexchange.com, Sept 2018. CC BY-SA.