TECOGEN TO PROVIDE ALTERNATIVE-SOURCE COOLING FOR CALIFORNIA'S LARGEST CIVIC BUILDING CONSTRUCTION PROJECT Tecogen's Natural-gas Powered Chillers to Offer Substantial Cost Savings and Environmental Benefits to Capitol Area East End Project WALTHAM, Mass., October 23, 2001 - Tecogen, a leading manufacturer of commercial and industrial natural gas-powered air-conditioners, shipped three TECOCHILL® systems this month for inclusion in the Capitol Area East End Complex - the largest civic building construction project ever undertaken in the state of California. The TECOCHILL systems, which run on natural gas instead of electricity, will provide air conditioning as part of a "hybrid" central utility plant for the complex. "Hybrid plants are emerging as one of the biggest trends in new building construction," says Bob Panora, president of Tecogen Inc. "More and more, we're seeing designers and consulting engineers specifying a combination of technologies to realize maximum flexibility and low operating costs for their clients." A hybrid plant alternates between different energy sources - such as electricity and natural gas - using whichever source is the most cost-effective at a given time. The three TECOCHILL systems will supply the centralized plant with 1,200 tons of cooling using natural gas, and are expected to operate year-round. Tecogen engineers estimate that the three systems could result in savings of about $75,000 per year. Tecogen's chillers allow commercial and industrial customers to significantly reduce their energy costs by running on natural gas, an abundant energy source that is efficient and environmentally friendly. The TECOCHILL systems have successfully met the most stringent air-quality standards in the United States. The Capitol Area East End Complex will comprise five office buildings with underground and aboveground parking and a separate parking structure, covering the five square blocks of land immediately east of the State Capitol building in downtown Sacramento. With approximately 1.4 million gross square feet, the complex will house the state's Departments of Education and Health Services - approximately 6,300 employees in all. About Tecogen Tecogen Inc. operates in the distributed generation market and is a leading manufacturer of natural gas-fueled commercial and industrial cooling and cogeneration systems. Tecogen has an installed base of more than 1,000 units, which it supports through an established network of engineering, sales, and service support. Formerly a public subsidiary of Thermo Electron Corporation, the company is now privately held. Tecogen is based in Waltham, Massachusetts, with annual revenues of approximately $13 million.