This is one bath the MTA wants to take.

The city transit agency yesterday unveiled a 48-panel solar-heating project atop its massive Coney Island subway-cleaning facility — already heating water to scrub down train cars.

The project produces about 2,000 gallons of 140-degree water a day — a temperature that can scrub even the most greasy D, Q, R, N and M subway cars during their weekly bath.

“When you look at the disaster in the Gulf, you understand that we have to reduce our reliance on fossil fuel,” said Richard Kessel, president of the New York Power Authority, which funded the project.