A respiratory treatment apparatus comprising: a power supply; a pressure generator configured to generate a flow of air; a first heating element configured to heat the generated flow of air; one or more sensors (4272, 4274; 5210, 5212, 5214, 5216, 5218) configured to generate sensor signals representing a property of the flow of air; and a processing system configured to: receive the sensor signals; based on the received sensor signals, determine a first control signal for controlling the first heating element; receive signals corresponding to current drawn by the pressure generator; receive signals corresponding to current drawn by the first heating element; based on the signals corresponding to current drawn by the pressure generator, the signals corresponding to current drawn by the first heating element, the determined first control signal for the first heating element, and power of the power supply, generate a new first control signal for controlling the first heating element; and control operation of the first heating element using the new first control signal for controlling the first heating element, wherein when current that would be drawn by the first heating element using the determined first control signal for the first heating element will cause current drawn by the respiratory treatment apparatus to exceed a maximum current of the power supply, the new first control signal is generated to reduce current drawn by the first heating element. a power supply; a pressure generator configured to generate a flow of air; a first heating element configured to heat the generated flow of air; one or more sensors (4272, 4274; 5210, 5212, 5214, 5216, 5218) configured to generate sensor signals representing a property of the flow of air; and a processing system configured to: receive the sensor signals; based on the received sensor signals, determine a first control signal for controlling the first heating element; receive signals corresponding to current drawn by the pressure generator; receive signals corresponding to current drawn by the first heating element; based on the signals corresponding to current drawn by the pressure generator, the signals corresponding to current drawn by the first heating element, the determined first control signal for the first heating element, and power of the power supply, generate a new first control signal for controlling the first heating element; and control operation of the first heating element using the new first control signal for controlling the first heating element, wherein when current that would be drawn by the first heating element using the determined first control signal for the first heating element will cause current drawn by the respiratory treatment apparatus to exceed a maximum current of the power supply, the new first control signal is generated to reduce current drawn by the first heating element. receive the sensor signals; based on the received sensor signals, determine a first control signal for controlling the first heating element; receive signals corresponding to current drawn by the pressure generator; receive signals corresponding to current drawn by the first heating element; based on the signals corresponding to current drawn by the pressure generator, the signals corresponding to current drawn by the first heating element, the determined first control signal for the first heating element, and power of the power supply, generate a new first control signal for controlling the first heating element; and control operation of the first heating element using the new first control signal for controlling the first heating element, wherein when current that would be drawn by the first heating element using the determined first control signal for the first heating element will cause current drawn by the respiratory treatment apparatus to exceed a maximum current of the power supply, the new first control signal is generated to reduce current drawn by the first heating element.