The York Wastewater Treatment Plant is a 26 million gallon per day (mgd) facility which removes a variety of contaminants from water to make it usable again, serving 170,000 residents of York, PA and surrounding communities. When energy bills at York Wastewater Treatment Plant topped $63,000 per month and service of the plant’s four internal combustion engines required a hefty 110 gallons (416 liters) of oil every 700 hours of operating time, York officials knew it was time to update the plant’s 23-year-old cogeneration system. The York City Sewer Authority selected a highly efficient Capstone CR600 Power Package that runs off the plant’s biogas and produces 600 kW of power. The waste heat from the turbines is used to heat the digester in a combined heat and power application. In addition, the Authority purchased a C1000 Power Package to produce 1 MW of power for demand response and backup power. Today, York officials estimate the Capstone cogeneration system generates more than 2.5-million-kW of electricity annually, reduces energy costs approximately $278,000 per year, and lowers carbon dioxide emissions by more than 1.5-million-pounds annually.