Princeton University has operated a campus-wide “district steam” system for over 150 years. Using a central cogeneration plant with underground steam distribution, it provides heat for campus buildings far more efficiently than individual heating systems would if they had been located in each building. But steam-heating is no longer considered state of the art and much of the existing infrastructure is very old and requires replacement. The University is now undertaking a campus-wide steam-to-hot-water conversion project that will modernize the district heating system and significantly improve its efficiency. The conversion is part of an overall effort that includes more thermal storage, geo-exchange, and solar photovoltaic power generation in the context of Princeton's Sustainability Action Plan. New buildings are being designed for hot water heating, and existing buildings will be converted from steam to hot water. The ultimate plan (over 30 years) includes full-campus conversion to hot water heating.

Two new energy facilities (TIGER and CUB) are being designed and constructed to provide new and converted campus buildings with hot water for heating and chilled water for cooling. These projects will provide the infrastructure to connect campus buildings to the new facilities. Using heat pumps and geo-exchange technology, these plants will be at the forefront of district energy technology. The existing energy facility will be maintained and partially converted to support the new system. The cogeneration plant (including new solar arrays) will continue to act as part of the Princeton Microgrid, providing a clean and highly reliable electricity supply to keep the campus (and the new hot water system) running regardless of weather conditions or power outages.

The project supports the University's shift toward more sustainable energy use and is a critical component in realizing Princeton's ambitious net carbon neutrality goal by 2046.