In this paper, we develop a solar exergy map concept and conduct a comprehensive case study to show how it is utilized and how it is significant for practical solar applications. Based on the exergy content of the solar radiation, the performance of a photovoltaic thermal (PV/T) system is evaluated for different Indian cities, namely Bangalore (latitude 12 degrees 58'N, longitude 77 degrees 38'E), Jodhpur (latitude 26 degrees 18'N, longitude 73 degrees 04'E), Mumbai (latitude 18 degrees 55'N, longitude 72 degrees 54'E), New Delhi (latitude 28 degrees 35'N, longitude 77 degrees 12'E) and Srinagar (latitude 34 degrees 08'N, longitude 74 degrees 51'E) for a year and for different cities of U.S.A., namely Chicago (latitude 41 degrees 50'N, longitude 87 degrees 37W), Las Vegas (latitude 36 degrees 10'N, longitude 115 degrees 12'W), Miami (latitude 25 degrees 46'N, longitude 80 degrees 12'W), New York (latitude 40 degrees 47'N, longitude 73 degrees 58'E), Portland (latitude 43 degrees 40'N, longitude 70 degrees 15'W), San Antonio (latitude 29 degrees 23'N, longitude 98 degrees 33'W), San Francisco (latitude 37 degrees 47'N, longitude 122 degrees 26'W), Tucson (latitude 32 degrees 7'N, longitude 110 degrees 56'W) and Tulsa (latitude 36 degrees 09'N, longitude 95 degrees 59'W) for different months of January, April, June and October. For the first time, the development of exergy maps for the exergy of solar radiation as well as the exergy efficiency of PV/T system is done for the above-mentioned Indian and American climatic conditions. It is found that the predicted exergy efficiency is in good agreement with the experimental results for the climatic conditions of New Delhi, India. It is observed that the average exergy efficiency is highest in Bangalore from January (28%) to April (32.6%) and from September (32.5%) to December (32.4%) and it is highest in Srinagar from May (29.5%) to August (26.8%) for Indian climatic conditions and for American climatic conditions, the PV/T system gives the best performance in terms of exergy efficiency in Las Vegas (32%) and Tucson (32.5-31.5%) in April and June. Copyright (C) 2009 John Wiley & Sons, Ltd.