A motor controller for an electric motor for driving a blower to generate an airflow. The motor controller includes a processor and a drive circuit configured to regulate power supplied to the motor to turn the blower. The processor computes a system resistance for the blower based on a fixed set point for a first control parameter and a feedback parameter. The processor receives an airflow rate demand value and computes an operating set point for a second control parameter based on the system resistance and the airflow rate demand value. The processor controls the drive circuit based on the operating set point to supply electrical power to the electric motor and to operate the blower to generate the airflow.