An example method includes: receiving, by an antenna of a receiver, RF power transmission waves from a transmitter, the RF waves forming controlled constructive interference patterns and destructive interference patterns in proximity to the receiver. The method also includes: transmitting, by the receiver to the transmitter, information used to determine a power level and efficiency of power received by the receiver device. The information that is used to determine the power level and efficiency indicates to the transmitter that the receiver device is receiving power at less than a maximum available efficiency. The method further includes: instructing a user of the receiver to change the receiver's position based on a comparison of respective voltage level or power received in each respective position or orientation of the receiver until a level of efficiency that is no less than the maximum available efficiency is achieved for the efficiency of power received.