Methods of reducing power consumption in a USB power-delivery source device. In one such method, one or more source capabilities messages are sent by the USB power-delivery source device. If, after sending a source capabilities message, a response to said source capabilities message is not received within a predetermined time period, the device sends another source capabilities message. If, after sending a predetermined number of source capabilities messages, no response is received, the device waits an extended period of time before sending another source capabilities message. Receiving functionality of the USB power-delivery source device is turned off during some or all of said extended period of time.