A control device, comprising an environmental sensor, an electrical quantity sensor, a control operating unit, and a resistance output unit. The control operating unit connects to the environmental sensor, the electrical quantity sensor, and the resistance output unit. The resistance output unit additionally connects to a temperature controller to replace original resistive temperature sensor. The resistance output unit outputs a first resistance to the temperature controller so that a controlled device operates at a first power state. The resistance output unit also can output a second resistance to the temperature controller so that another controlled device operates at a second power state. When the control operating unit reads environmental information or time information, the resistance output unit outputs the first resistance or the second resistance after calculating by the control operating unit so that the controlled device operates at the first power state or the second power state.