In India the performance of buildings may take a greater significance in near future with the constraint of limited resource availability, domestic and international targets for the reduction of green house gas emissions. For India, annual cooling degree days are 3120 and annual heating degree days are 80. In this study, cooling degree days for Tiruchirappalli, a location in south part of India is found using the long-term recent measured data by British gas method. Cooling degree days are calculated for eleven base temperatures ranging from 18 C to 28 C and are tabulated. Annual cooling degree days is related with base temperature for Tiruchirappalli with the correlation coefficient of 0.995. Also, an empirical relation between the month and monthly average cooling degree days is obtained with the correlation coefficient of 0.942. Heat loss calculations are carried out for Indian buildings as a function of annual cooling degree days for different U values of buildings. The results are compared between the best and worst U values of the buildings. The calculations are also made for heat loss for different base temperatures keeping the U value of the building constant. The results indicate that either a correction in base temperature or a better U value for the buildings will save energy up to an extent of 80% in air-conditioned Indian buildings.