The Island Princess was the first to connect to the new shore power technology at Pier 27. It allows the ship to turn off their giant polluting diesel engines and draw from the city's clean energy power grid.
The mayor says besides being environmentally friendly and it's cheaper.
"It works out to about $16,000 in terms of the cost for the cruise ship and its parent company as opposed to spending $18,000 for traditional diesel and polluting the northern waterfront," Gavin Newsom said.
The Port of San Francisco project is only the fourth in the world to develop shore power for large cruise ships.