Next week's public hearing on Tata Power's proposal to convert its 500 Mw unit at Trombay in this metropolis' northeast to coal-based from oil and gas is expected to be stormy.
The Maharashtra Pollution Control Board has scheduled the hearing on January 15.
Political parties and environment experts have expressed reservations on the company's move.
The ruling Congress and Nationalist Congress Party, and the opposition Bharatiya Janata Party, have said they'd present their stand during the hearing.
The Shiv Sena has openly opposed the proposal, saying it would further pollute the city, create health problems and mean a rise in power supply rates.
Tata Power says adequate measures have been taken to protect the environment and the proposed modernisation, of unit 6, would provide relief to consumers on power rates.
The per-unit cost of electricity is estimated, it says, to come down to Rs 4.48 in 2015-16, while the cost due to oil and spot gas pushes the present generation cost higher than Rs 8.50 a unit.
Environmentalist Debi Goenka termed the move a retrograde one.
He told Business Standard: "Globally, when alternative energy source-based power projects are being considered, Tata Power is converting unit 6 to coal.
"Its transportation and use will damage the environment and consumers will also have to bear an additional tariff (rate) burden, as Tata Power has proposed an investment of Rs 1,174 crore (Rs 11.74 billion)