A wireless receiver for use with a first electromagnetic resonator coupled to a power supply, the first electromagnetic resonator having a mode with a resonant frequency ω1, an intrinsic loss rate Γ1, and a first Q-factor Q1=ω1/2Γ1, and the wireless receiver includes a load configured to power a system using electrical power, a second electromagnetic resonator configured to be coupled to the load and having a mode with a resonant frequency ω2, an intrinsic loss rate Γ2, and a second Q-factor Q2=ω2/2Γ2, wherein the second electromagnetic resonator is configured to be wirelessly coupled to the first electromagnetic resonator to provide resonant, non-radiative wireless power to the second electromagnetic resonator from the first electromagnetic resonator; and a communication facility to confirm compatibility of the first and second resonators and provide authorization for initiation of transfer of power.