The largest energy efficiency project that the New York Metropolitan Transportation Authority (MTA) has ever undertaken with the New York Power Authority (NYPA) is under way in Grand Central Terminal, which will reduce annual carbon emissions by 10,000 tons.

Behind-the-scenes equipment that keeps Grand Central cool in the summer, warm in the winter and flushed with fresh air all year round is being upgraded though a $22 million partnership between NYPA and MTA Metro-North Railroad. The energy efficiency project will conserve energy and save an estimated $3 million a year.

Deep below the gleaming marble concourse and high above the constellation ceiling is a myriad of pumps, chillers, fans, compressors, cooling towers, meters and miles of high-pressure steam pipes, many of them a century old. Many of these systems are being replaced throughout the 48-acre terminal that extends seven stories above ground and 150 feet below sea level.

The upfront costs of the new, energy-efficient equipment will be borne by NYPA and be repaid annually over about 11 years by Metro-North with the money it saves as the result of a reduction in energy use. Installation began this month and will be completed by the end of 2013.

Over the past year, Metro-North undertook $1.5 million in energy efficiency improvements in Grand Central including 11 new escalator controllers that save 25-40% in electricity, 2,600 new lighting fixtures, 59 new motors of 5 horsepower or greater and a new sewage ejector. Meters also were installed on the steam, chilled water, compressed air and gateway electric feeders to collect data for the metering and verification portion of the project.