Williams College has performed a carbon emissions inventory in partnership with Williamstown, which established that approximately 34,700 tons of carbon dioxide emissions are produced annually as a result of campus energy use. In order to lower that figure, the College switched to an energy supplier with lower emissions, bought enough renewable energy to power its Environmental Studies Center, and installed a 7.2 kilowatt solar array on its science center. Eight-hundred lightbulbs have been switched to compact-fluorescent, and the cogeneration plant, which was upgraded in 2002, is more efficient than conventional plants. A small, solar water-heater is to be installed on one residence hall, and a test tower has been installed to investigate the feasibility of a wind farm near campus.