Described herein are embodiments of a source resonator coupled to an energy source generating an oscillating near field region; and at least one device resonator optionally coupled to at least one energy drain and freely moving within the near field region of the source resonator. The source resonator and the at least one device resonator may be coupled to transfer electromagnetic energy wirelessly from said source resonator to said at least one device resonator as the at least one device resonator moves freely within the near field region, where the source resonator and the at least one device resonator may be coupled to provide κ/sqrt(Γ1Γ2)>0.2 over an operating region.