Boston explores sea- and river-source heat pumps for big buildings

Boston is testing a new way to heat and cool large buildings: pulling thermal energy from the harbor and nearby rivers. A heat pump moves heat from one place to another to warm or cool a space, and water holds heat more steadily than air, staying cooler in summer and warmer in winter. That makes rivers and harbors an efficient source, especially in a dense, old city like Boston where digging for conventional ground-source geothermal systems is difficult or costly.

Three projects are underway. The Boston Area Thermal Energy Network Project, launched in late July, is studying how to draw heat from Boston Harbor, the Fort Point Channel, and the Charles and Mystic rivers to serve large institutions; final recommendations are expected by summer 2027. The University of Massachusetts Boston, which has used seawater for cooling since the 1970s, is now adding equipment to also pull heat from the water for winter heating, aiming to cut natural gas use by 82 percent across 12 buildings. And Vicinity Energy is building a 35-megawatt river-source heat pump on the Charles River, expected to be the largest in North America, to supply steam heat to its institutional customers in Boston and Cambridge.

These projects target large institutions, not individual houses, so they will not directly change what a homeowner installs. But they signal growing momentum for water-based heat pump technology in the region, which could eventually shape local energy infrastructure and climate goals.