The scope of this SAE Recommended Practice is to establish uniform test procedures and minimum performance requirements for passenger car windshield defrosting systems. It is limited to tests that can be conducted on uniform test equipment in commercially available laboratory facilities. The test procedures and minimum performance requirements, outlined in this recommended practice, are based on currently available engineering data. It is the intent that all portions of the recommended practice will be periodically reviewed and revised as additional knowledge regarding vehicle defroster performance is developed.