The scrip plummeted 11.43 per cent to close at Rs 117.05 on the BSE, after touching an intra-day low of Rs 116.60. The company's shares had opened at Rs 129.60, also its intra-day high.
On the National Stock Exchange (NSE) too, shares tumbled 11.48 per cent to close marginally higher at Rs 117.25. It touched a 52-week low of Rs 116.35 on the bourse.
The scrip opened at Rs 128.50, also the intra-day high.
Central Electricity Regulatory Commisson (CERC), which notified the new tariff norms, has made changes to incentives system for thermal power plants as well as to calculation of taxes.
"... NTPC would be worst hit due to across-the-board cut in its incentives," global brokerage firm Bank of America Merrill Lynch said in a report today.
State-owned NTPC has an installed power generation capacity of more than 42,000 MW.