Water Main Geothermal
A report by Lilli Ambort and John Farrell, released October 2020
Municipalities across the U.S. have an opportunity to leverage the potential energy lying under their streets to reduce pollution, cut energy bills, and affordably transition away from fossil gas.
Special thanks to Jay Egg for contributing his knowledge on geothermal heat pumps and assisting with the review of the piece. Additional thanks to Jack DiEnna, Liu Xiaobing, and Don Penn for contributing their knowledge on geothermal systems and David Howard for contributing knowledge on air source heat pumps.
This brief explores a novel, affordable concept to reduce greenhouse gas emissions and other pollutants from home heating and cooling: water main geothermal. Air source heat pumps can replace existing fossil-powered systems, but struggle to compete cost-effectively in cold climates. Water main geothermal combines the efficiency and technical capability of ground-source geothermal in cold climates with costs competitive to fossil gas furnaces. Using a heat exchanger attached to the water main (or a short spur), this mechanism replaces expensive well drilling or expansive loop fields to deliver thermal energy to a building’s geothermal heat pump.
This analysis shows that water main geothermal could provide a viable, cost-effective alternative to traditional home heating and cooling systems. Homeowners benefit from lower heating and cooling costs, water utilities benefit from a new source of income, and cities benefit from reaching their climate commitments. It is our hope that U.S. cities –– that almost universally own their public water utility –– use the results of this brief to conduct a feasibility study to explore deployment of water main geothermal to homes and businesses in their jurisdiction.