This paper describes the test methodology developed for evaluation of defrost and demist system performance. Test conditions for testing defrost and demist system and evaluation criterion is as mentioned in Automotive Industry Standard AIS 084. The paper describes the process of development of test set up and a test method for testing of defrost and demist systems. We initially started with particular method of performance evaluation including method of area measurement. Subsequently we evolved a method of performance evaluation using image analysis technique. This paper covers comparative study on methods of measurement.