A calibrated model has been used to estimate the energy savings by cool roof application on buildings located in five different climatic zones.  The model has been calibrated as per the measured data in a building located in Hyderabad (India), and the same has been used to project energy savings in different cities located in five different climatic zones of the country.  Results show that the maximum reduction in energy consumption is observed in Mumbai (warm and humid climate), followed by Ahmedabad (hot and dry climate), Bangalore (temperate climate), and Delhi (composite climate).  Least energy saving is observed in Shillong (cold climate). In all the climates except cold, the financial payback period is acceptable, being less than 3 yr, whereas for cold climate, the investment is getting paid back in 6.69 yr, making the cool roof application not very attractive.