# powerMonitor > Monitor power state changes. You cannot require or use this module until the `ready` event of the `app` module is emitted. For example: ```javascript const electron = require('electron') const {app} = electron app.on('ready', () => { electron.powerMonitor.on('suspend', () => { console.log('The system is going to sleep') }) }) ``` ## Events The `powerMonitor` module emits the following events: ### Event: 'suspend' Emitted when the system is suspending. ### Event: 'resume' Emitted when system is resuming. ### Event: 'on-ac' _Windows_ Emitted when the system changes to AC power. ### Event: 'on-battery' _Windows_ Emitted when system changes to battery power.