This paper presents the results of the performance enhancement study in 22 coal fired thermal power stations of capacities 30-500 MW. The efficiencies and performance indices of the equipment are evaluated which then leads to the performance evaluation route-operational optimization, simple modification of equipment or renovation. The generic problems associated with design, operation and fuel inputs is investigated and appropriate solutions are suggested to improve the boiler efficiency levels from 71-86% to 86-87% immediately and 89-90% on a long term (5-10 yr) basis. A large volume of design and operating data has been analysed and presented in the form of curve fits for computer simulation of the performance of boilers for high ash coals.