Phones are rarely plugged in unless the battery is dead. This strategy actually works with laptops though. I know that one company set up all their laptops to

Phones are rarely plugged in unless the battery is dead. This strategy actually works with laptops though. I know that one company set up all their laptops to stop drawing power from mains and run from the battery at peak hours, even though it was still plugged in. This was for cost savings and not for environmental ones, but the same strategy would work.