On/off fan speed control uses a thermostat to toggle a fan's operation based on a set temperature. As the temperature exceeds the set point, the fan runs at full speed until it drops below that threshold, at which point it stops. This method offers various benefits, including simplicity, cost-effectiveness, and energy savings. It's ideal for environments with low thermal mass or non-critical temperature control, and it's particularly advantageous in places with significant temperature variations, like Toronto, to prevent overcooling.