A positive airway pressure (PAP) device for supplying a flow of breathable gas to a patient includes a flow generator configured to pressurize a flow of breathable gas and a humidifier configured to receive and humidify the pressurized flow of breathable gas from the flow generator. The PAP device also includes a power source. The flow generator, humidifier and power source are positioned so that heat generated by at least one of the flow generator and the power source is conveyed to water in the humidifier.