Note that 'dumb' USB chargers don't use anything close to their charging power when idle. See Ken Sheriff's fantastic USB charger teardown - http://www.righto.c

Note that 'dumb' USB chargers don't use anything close to their charging power when idle. See Ken Sheriff's fantastic USB charger teardown - http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-ap... In that article, he measures the idle power usage of a bunch of chargers. Some use as little as 19 milliwatts. The electricity cost of leaving that charger plugged in all year is miniscule.