This can be mostly true already. If you look at Ken Shirriff's analysis of chargers here: http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.h

This can be mostly true already. If you look at Ken Shirriff's analysis of chargers here: 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... The best charger that he analyzed was a Samsung oblong charger that had a vampire draw of 18mw. At 18mw, if it was plugged in all year without doing any charging, it would consume a total of .12 kilowatt-hrs of electricity. $0.01/yr is pretty close to zero power use. There's no theoretical reason that figure could not be improved upon. However, it is probably the wrong end to optimize on. From the same post, you'll see that the BEST of these chargers was 80% efficient under load, meaning when it's actually in use, it's only putting 80% of its draw into the device. If it were charging only 1 hour per day, at its in-use draw of 2.4A, 21 kilowatt-hours are lost per year doing the actual charging, at a cost of $2-3 per year (in the US).