An electronic device including wireless energy receiver circuitry and an energy receiver antenna that is connected to the wireless charging circuitry can be used to improve electrical efficiency. The energy receiver antenna has a tunable reception frequency that can be controlled to optimize energy reception. For example, the energy receiver antenna can be tuned to match a wireless transmission frequency being output by the electronic device itself. If the electronic device is not currently outputting any transmission signals, the energy receiver antenna can be tuned to optimize energy reception from any other available signal source. In some examples, the electronic device may dynamically tune the reception frequency of the energy receiver antenna according to the relative strength of signals being received. Energy received by the energy receiver antenna can be supplied to power various components of the electronic device.