For the last six years, the city has mandated that owners of buildings bigger than 50,000 square feet report energy and water usage to establish benchmarks. Though compliance was initially good, Knapp said, it has waned among some owners. The city could use the money for a program that requires commercial properties to make energy changes without requiring major retrofits. For example, she said, some buildings run air conditioning all weekend even though few workers are in the building. Cutting that down could save 5 percent to 20 percent of total energy use without much cost.