New York City Mayor Zohran Mamdani wants to put the heat that makes the city’s subway unbearable every summer to work. The city, New York Governor Kathy Hochul and the Metropolitan Transportation Authority (MTA) have announced a study into a thermal energy network (TEN) at the Brooklyn Bridge-City Hall and Chambers Street station complex in Lower Manhattan. The plan is to pull heat off the platforms in summer, store it deep underground, and use it to warm nearby city buildings in winter.The $800,000 feasibility study is funded by the New York State Energy Research and Development Authority. If the system is built, it would be the first thermal energy network in any US transit system. Mamdani made the announcement from a steamy platform inside the complex, which he called a “chamber of horrors”. Brooklyn Bridge-City Hall averaged 96°F (about 35.5°C) through summer 2025, making it one of the hottest stations in New York.
Subway heat would be stored 600 feet below Chambers Street station
Radiant cooling panels would absorb heat from the Brooklyn Bridge-City Hall platforms, which serve the 4, 5 and 6 lines, and possibly from the Chambers Street J/Z platforms too. These panels circulate chilled water through walls, ceilings or floors, so the cool surfaces soak up heat directly. Officials say this can be 25 to 35% more energy-efficient than traditional air conditioning.The captured heat would travel through pipes to geothermal boreholes drilled 500 to 600 feet beneath an abandoned centre platform at Chambers Street. Since nobody uses that platform, the MTA can test the system without disturbing the more than 18,000 riders who pass through the station on an average weekday.
City Hall could be heated with waste heat from the New York subway
In winter, the stored heat would be piped to City Hall, the David N. Dinkins Municipal Building, Tweed Courthouse and Surrogate’s Court. Mamdani said heating the Municipal Building alone costs the city about $1.4 million (roughly Rs 12 crore) a year.The same technology already runs at St Patrick’s Cathedral and the New York Botanical Garden, besides several hospitals and universities. A subway station is a tougher job. “Bringing down the temperature is a real challenge in a century-old system with open entrances and vents everywhere,” MTA chair and CEO Janno Lieber said.Part of the problem comes from the trains themselves. Air-conditioned cars vent their hot air into stations and tunnels. At Brooklyn Bridge-City Hall, trains waiting at the 6 line terminal add even more heat. Mamdani said some stations get up to 20 degrees hotter than the street above, adding that commuting in his wool suit is “far from a therapeutic experience”.
Mamdani’s subway cooling plan now depends on what lies beneath Chambers Street
The contract for the feasibility study is expected to be awarded this fall. If the ground beneath Chambers Street proves suitable, design work would begin in early 2027.The study runs alongside a separate renovation of the Chambers Street station, which opened in 1913 and has long been one of the most neglected stops in the system. That project, paid for through congestion pricing, will fix leaks, replace tiles and mosaics, and upgrade stairways and lighting.Not every rider is convinced the money is well spent, and the MTA still says the quickest relief is getting people onto air-conditioned trains faster. Lieber kept his own expectations modest. Bringing the platforms down by even a few degrees, he said, would be “the difference between total misery and merely sweltering”.
