Methods and apparatus include a hair iron having a controller and a heater between first and second arms movable relative to each other between open and closed positions. The controller connects or not the heater to a line voltage to heat hair when placed between the arms during use. A proportional-integral-derivative (PID) controller communicates with a thermistor measuring a current temperature of the heater and makes requests of the controller to operate the heater at a setpoint temperature. In various embodiments, the heater heats to full power during warm-up and operates thereafter at lower temperatures based on a reading of the line voltage and a time to adjust the current temperature to the desired setpoint temperature.