Idea of Quick Mode On Icon
It's the picture of a lightning bolt to indicate electricity. It is a single bolt of lightning, with no clouds or other features. It looks like the image of an hourglass, tilted about 45 degrees up, and then stretched out until it resembles a lightning bolt.
This page shows the different variations of the Quick Mode On from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.