Technical and environmental efficiency of some coal-fired thermal power plants in India is estimated using a methodology that accounts for firm’s efforts to increase the production of good output and reduce pollution with the given resources and technology. The methodology used is directional output distance function. Estimates of firm-specific shadow prices of pollutants (bad outputs), and elasticity of substitution between good and bad outputs are also obtained. The technical and environmental inefficiency of a representative firm is estimated as 0.10 implying that the thermal power generating industry in Andhra Pradesh state of India could increase production of electricity by 10 per cent while decreasing generation of pollution by 10 percent. This result shows that there are incentives or win-win opportunities for the firms to voluntarily comply with the environmental regulation. It is found that there is a significant variation in marginal cost of pollution abatement or shadow prices of bad outputs across the firms and an increasing marginal cost of pollution abatement with respect to pollution reduction by the firms. The variation in marginal cost of pollution abatement and compliance to regulation across firms could be reduced by having economic instruments like emission tax.