A heating system includes a heater, a switch providing alternating current to the heater, and a current sensor electrically connected between the switch and the heater. The heating system also includes a controller that controls operation of the switch. The controller activates the switch during a portion of a half cycle of the alternating current having increasing amplitude under a threshold. The controller determines, based on a signal received from the current sensor during the activation of the switch, a time period from the start of the half cycle to a threshold timing at which the alternating current reaches the threshold. The controller reactivates the switch at a timing on or after a timing obtained by subtraction of the determined time period from an end of the half cycle. The heating system is useable within an image forming apparatus.