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Life-cycle cost analysis: ground-source heat pumps save energy but add large upfront costs, committee told
Summary
Design and sustainability teams told the committee that ground‑source heat pumps offer lower lifetime energy use but carry roughly $23–28 million higher upfront installation costs (before incentives) than air‑to‑water heat pumps; hybrid approaches and incentives could narrow that gap but further study is required in schematic design.
Medford — At the June 1 meeting of the Medford Comprehensive High School Building Committee, the project team presented a 50‑year life‑cycle cost analysis comparing renovation and new‑construction options and three HVAC approaches, concluding that all‑electric heat‑pump systems can meet the project’s energy goals but that full ground‑source (geothermal) systems carry large incremental installation costs.
Sustainability director Martine Dion and consultants compared the B1.2 renovation/addition and the D1.1 new‑construction options with two HVAC system families: ground‑source heat pumps and high‑efficiency air‑to‑water heat pumps. Ground‑source systems achieve slightly better energy efficiency (lower energy‑use intensity) and modestly lower operational carbon, but the consultants estimated an installation premium on the order of $23–28 million for full ground‑source systems compared with air‑to‑water alternatives.
“Overcoming the estimated 23 million plus incremental cost between the ground source heat pump and the airto water heat pump is challenging,” the team said, adding that projected replacement costs, maintenance savings and Mass Save incentives (roughly a few million dollars in preliminary estimates) do not fully offset the upfront premium over a 50‑year horizon.
The team said a full geothermal borefield would likely require about 10–15 acres of site area at the proposed campus; a hybrid approach — combining surface heat pumps with a reduced geothermal field — could reduce required borefield acreage to roughly 5–8 acres and lower the incremental capital cost. The consultants also forecasted an energy‑use intensity goal near 35 kBtu/sq ft for the new designs and estimated that rooftop and canopy PV could supply a substantial fraction of on‑site energy (a high canopy could produce roughly half of a ~6.2 MW target while low‑angle roof PV would produce closer to 20%).
The project team emphasized the next decision point: HVAC selection and final LCCA will be refined during schematic design. The committee was told incentives under Mass Save and potential federal programs such as those created under the Inflation Reduction Act remain subject to confirmation and timing, which will affect the final economics.
What’s next: The team plans further analysis during schematic design and recommended the committee consider hybrid HVAC approaches that reduce acreage needs and initial costs while preserving long‑term energy benefits.
