Starting from 2024, NYC buildings will be forced to meet certain emission limits. Otherwise, they will be charged a penalty of $268/year for every metric ton of CO2 equivalent above the limit. Emissions can be reduced by improving energy efficiency in buildings, but switching to cleaner energy sources is also a viable strategy. For example, natural gas is a cleaner option than #2 fuel oil, and onsite solar power is cleaner than electricity from the grid.