NYC is now the largest city in the U.S. to enact legislation relating to the electrification of buildings.
On December 15, 2021, the NY City Council voted in support of Int. 2317A-2021, which effectively mandates the electrification of most new buildings by prohibiting the on-site “combustion of a substance that emits 25 kilograms or more of carbon dioxide per million British thermal units of energy.”
Former Mayor Bill de Blasio, a proponent of legislation to promote the electrification of NYC buildings, signed Int. 2317A-2021 (subsequently Local Law 154 of 2021) on December 22, 2021. 
Local Law 154 of 2021 is the amended and enacted version of Int. No. 2317 introduced by Council Member Alicka Ampry-Samuel (D-City Council District 41) on May 27, 2021. The law, which expanded the number of exceptions in the original bill, now applies to new buildings less than seven stories for which an application for the approval of construction documents is submitted after December 31, 2023, and to new buildings seven stories or more for which an application is submitted after July 1, 2027. Emergency or standby power is allowed for all covered buildings, which is an important option, especially for critical infrastructure and high-rises in NYC. Local Law 154 of 2021 also includes the following exceptions:
- Buildings (excluding those classified as R-3) in which the allowable amount of carbon dioxide emissions is exceeded in order to provide hot water and for which the approval of construction documents is submitted on or before July 1, 2027. (R-3 refers to one of 10 residential zoning districts in NYC. R-1 is the lowest density and R-10 is the highest density. For details on R-3 residential districts, see this NYC Planning website on Zoning).
- Buildings less than seven stories in which 50% or more dwelling units are officially designated as affordable housing and for which an application for the approval of construction documents is submitted before December 31, 2025.
- Buildings seven stories or more in which 50% or more dwelling units are officially designated as affordable housing and for which an application for the approval of construction documents is submitted before December 31, 2027.
- Buildings “that will be primarily used by a utility regulated by the public service commission for the generation of electric power or steam.”
- Buildings where compliance with the allowable limit of carbon dioxide emissions is not feasible, such as those used for manufacturing, hospitals, laboratories, commercial kitchens, and laundromats.
Retrofits are not mentioned in Local Law 154 of 2021; however, the NYC BUILDINGS BULLETIN 2016-012 (nyc.gov) specifies when “an extension, elevation, renovation, etc. is to be considered a new building.” If a proposed retrofit is defined as a new building, the owner must obtain a new building permit from the NYC Department of Buildings and comply with Local Law 154 of 2021.