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Re:Ultrasonic Power Transfer Investigated Using Data from uB... by rootedbox on Tuesday October 20, 2015 @04:38PM (#10421654)
you would also be spending $200 extra on your electric bill
Re:Ultrasonic Power Transfer Investigated Using Data from uB... by Retric on Tuesday October 20, 2015 @05:23PM (#10421905)
At 1% efficiency that's 30w or ~= 6 cents per day if your paying 10c/kwh. So, efficiency is only really important if it's crazy terrible.

PS: I suspect the real issue is making a receiver fit into a reasonable cellphone case.