Thermal Energy Network Planning

At a glance

What: the city's effort to plan a neighborhood-scale thermal energy network (shared underground heating and cooling loops) as a way to move existing buildings off gas. A feasibility study of a geothermal pilot (Pacific Street Park in Cambridgeport as the case studied in depth) was reviewed at a committee hearing on Oct 20.
Where it stands: the study found the land, street space, ownership and economics are the hard parts (about 30 years to recoup capital with current incentives). Advocates from HEET and Black Swan Lab challenged its assumptions (boreholes only, no Harvard or MIT land, retrofit costs counted as extra). Nolan, the committee chair, signaled she wants to reconvene the group.
Next: study reports and assumptions are to be made public; Eversource is to follow up on how avoided grid costs and Cambridge's gas-island status figure in its planning; Black Swan Lab cost papers were promised within about two weeks; federal tax credits start sunsetting in 2032.

Technical consultant: Salas O'Brien, funded mainly with federal pandemic-relief money. A network at this scale needs about an acre for a borefield (550 to 850 foot bores), pipes under streets, and heat pumps in each building.
Of 38 candidate sites, most were parks; private lots were judged unlikely to stay open for a 50-year asset. Ownership and operation, and aligning many private owners on different equipment timelines, were the main obstacles.
Pacific Street Park pilot concept: a hybrid design about 99% geothermal; most cost is converting buildings. Public figures quoted in the hearing ranged around $50 to $70 million (class five, very rough estimate); the low end is a bit under double the cost of Eversource's Framingham pilot.

Cost assumptions and transparency: HEET, Black Swan Lab, a GeoMIT student leader and Zusy asked for the analysis to be shared and peer reviewed.
Boreholes are the most expensive source; wastewater, waste heat and aquifers may cost less. Any network still needs piping to move heat.
Who owns and operates it: utility-owned (as in Framingham, paid by ratepayers), a private operator, or the city; affordability and long-term contracts if private.
Counting health costs of gas and grid savings (avoided substations) in the economics; no mechanism exists yet to assign grid savings to a project.

Eversource's network: about 135 customers, 88 boreholes in three borefields, commissioned December 2024, ratepayer funded; about $28 million spent of roughly $30 million, with a federally funded expansion and a new-construction filing pending at the state utility regulator.

About 78 minutes across 1 meeting (from transcript timestamps; approximate).

Meeting	Minutes
2026-10-20 - Health and Environment Committee	78

2026-10-20 - 2026-10-20 - Health and Environment Committee — Hearing on thermal network planning: city study presented, HEET and Black Swan Lab critique, Eversource, Vicinity, MIT and Boston study presentations, three public comments; no votes.