> we agree at least here that most people don't think about the cost of plugging in a phone to charge

We agree because it’s smaller than they should care about.

Even at 50% socket to battery efficiency and $0.20/kWh electricity, completely charging a 10-15Wh battery costs under a penny.

I won’t bend over to pick up a clean but wet penny off the sidewalk, let alone go without a charged phone to save a penny.