Physics is a prestigious subject. It has many branches. One of the emerging branch is energy physics.Sun is the source of energy. Making use of this renewable energy will reduce our cost and labor. Countries like India,we get plenty of sunlight.This natural fuel comes into our house in the form of solar cookers. Solar cooker is a gift for fuel consumption.It was found that cooking at late nights will be possible by using Phase Change Materials(PCMs). This book deals with the fabrication of cost effective box type solar cooker with PCM. In this study paraffin wax was used as the PCM. The efficiency of the cooker with different loads of water and with different loads of paraffin wax were studied. It was found that there is a relationship between the amount of PCM and the efficiency of the cooker.