Does it really make that difference? iPhone uses about 1 kwh to power up for a whole year. To put that into perspective, that’s the amount of electricity you’d need to power ten 100-watt incandescent lightbulbs for an hour.

This is purely a PR move. Might as well have made it a dummy button and no one would’ve batted an eye.

Edit: power up 1 year = fully drain the battery and re-charge it everyday.