A wireless power transmitter and receiver, and related methods are provided. In one embodiment, a wireless power receiver may include: a receiving unit configured to receive wireless power from a source resonator; a detecting unit configured to detect a current value, a voltage value, or both of the wireless power; a controller configured to determine whether the detected current value, the detected voltage value, or both have a peak value, in a relation to a load which the wireless power is to be transmitted to; and a communication unit configured to transmit a result of the determination to the source resonator.