Updated to correct the total power output expected from the MTA rooftop project.

Electric cars and public transportation go together in more ways than one.

In the latest example, the New York Metropolitan Transportation Authority plans to add solar panels to the rooftops of its rail yards and bus depots to help feed the local power grid.

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The MTA started last Monday with requests for bids on seven properties belonging to NYC Transit, the Long Island Rail Road, and the Metro-North Railroad in Westchester County. The proposal envisions expanding that collection to plans for dozens of MTA buildings that constitute more than 10 million square feet of space for solar panels that can deliver up to 100 megawatts of power, enough to run 18,000 New York households.

Some of those households may have electric cars that could benefit from extra power on the grid.

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"Green energy always had a dual benefit—it can help save the planet and it can be a big money-maker as well,” MTA Chief Development Officer Janno Lieber said in a statement.

Though the benefits of renewable energy are clear, the MTA could also use the money. It is reportedly facing $42 billion of debt by 2022.