Steam rises in New York. Photographer: Robert Nickelsberg/Getty Images
A network of underground pipes has pumped steam into a spattering of Manhattan buildings for more than 140 years, quietly powering their heating and cooling systems with little fanfare, save for the occasional orange steam stack dotting the island’s streets.
Now, as the biggest US city seeks to curb its carbon emissions, that 106-mile subterranean network delivering 370-degree vapor to a small subsect of New York’s skyline may have a bigger role to play.
The system, operated by New York-area energy provider and utility Consolidated Edison Inc., delivers about 15 billion pounds of steam every year from the southern tip of Manhattan all the way up to the 90s near the upper half of Central Park. It’s one of hundreds of century-old steam systems still operating across the US in dense downtowns as well as at mega-facilities like college campuses and airports — and by far the country’s biggest.
In NYC, steam’s customers tend to punch above their weight when it comes to landmarks, including the Empire State Building, the United Nations and Madison Square Garden, home to the New York Rangers and Knicks. Still, steam is dwarfed by other forms of energy. The system supplies just over 1,500 customers in NYC, a fraction of the millions served by Con Ed’s electric and gas systems. And while the pipe network has grown considerably since its 1882 launch, when it included just three miles of main piping in the city’s Financial District, it hasn’t had a major expansion to its customer base in years.
That may be about to change. “With a lot of the new legislation as well as the New York state goals for the clean energy future, we do predict that we will have a growth trajectory where we will be getting more customers,” said Amy Haag, vice president of steam operations at Con Ed. Especially for buildings operating their own boilers or cogeneration units and looking to decarbonize, “we are a pretty desirable commodity.”
Although the vast majority of New Yorkers don’t live in apartments or work in office towers connected to the steam system, many will be familiar with the solid orange or striped stacks that occasionally pop up on the city’s streets and sidewalks, releasing giant plumes of vapor. Built tall enough that the steam won’t impede driver or pedestrian visibility, the stacks are used as a temporary venting system when rain water or other liquid comes in contact with the main steam pipes. They’re such an iconic part of the New York City scenery that they’re often put in films by Hollywood set crews trying to evoke the feel of Manhattan.
Many of the US’s other systems, sometimes called “steam loops,” are also working to decarbonize. Vicinity Energy Inc., which operates systems in a dozen US cities, has committed to electrifying its entire portfolio by 2050 — including in the greater Boston area, where its steam pipe system delivers heat to some 70 million square-feet of building space. The company installed an industrial-scale electric boiler at its combined heat and power generation facility in Cambridge in 2023, deemed a critical step to producing carbon-free steam. It also plans to add a massive heat pump that will harvest thermal energy from the Charles River.
“Systems in place are continuously being modernized, optimized and updated,” said Rob Thornton, president and CEO of the International District Energy Association, an industry group for suppliers of energy services to buildings. “A plant can integrate a series of technologies like electric boilers, heat pumps, thermal storage and integrating renewables.”
Back in New York, the 2019 passage of Local Law 97, which sets strict emission limits on many city buildings, lays the groundwork for a growing interest in steam. Buildings account for about two-thirds of greenhouse gas emissions in New York City, so cutting their carbon footprints has been a priority for green-minded lawmakers. Under the law, steam is the lowest greenhouse-gas-emitting energy source per unit of energy, executives from Con Ed said on a webinar.
And it may be about to get cleaner. A joint proposal adopted by the state’s Public Service Commission includes preliminary work on an industrial heat pump project at the East River Station for $3 million and a feasibility study for a thermal storage project, among other things. Today, the steam is primarily heated with natural gas, or some fuel oil in the very dead of winter. It’s been converting the plants’ oil-burning backup systems to run on No. 2 fuel oil, which emits less than the No. 4 oil used previously.
For now, Con Ed’s steam system is entirely focused on Manhattan, where the main steam pipes already exist. Expanding into other boroughs would require crossing a river, making it much more challenging — though not necessarily impossible for a company that owns small pieces of real estate in other boroughs. “While nothing is official in the future, if there was an interest in it, the next move would be to areas close to our facilities in Brooklyn and Queens after we built out some more of our facilities there,” Haag said, without naming a timeline for any kind of major expansion.
For now, any growth would need to start small. “You can imagine the challenges to creating a whole piping network that goes below the surface of the streets,” she said. “We kind of have to take our footprint now and slowly build it and expand it from the epicenter outward.”