I don't have that option on my car so don't have any particular knowledge of it other than what I read in the FSM. For what it's worth, the following is what the manual says:
The heated windshield system quickly clears ice from the windshield in severe weather. The window contains a transparent resistive coating. The coating heats when power is applied to it. Power for the system comes directly from the generator. The engine must be running for the system to operate. The system consist of special windshield, heated windshield control module, heated windshield switch, and a special generator. The transaxle position switch is used as an input to the system.