Local Law 97 of 2019 puts annual greenhouse-gas limits on most New York City buildings over 25,000 square feet. The limits started in 2024 and tighten from 2030. Chiller plants are among the largest electric loads in the buildings it covers. Here is where chiller and cooling-tower efficiency fits, based on the Department of Buildings' own reporting.
What the first year showed
The DOB's report on the 2024 compliance year, published in 2026:
- 19,963 properties, representing 29,031 buildings, were required to report. About 95% filed.
- Among Article 320 properties that filed with emissions data, 95% met their 2024 limits. 470 were above them: 149 by less than 10%, 197 by 10–50% and 124 by more than 50%.
- About a third of those over the limit requested penalty mitigation under the good-faith-efforts pathway.
The 2024–2029 limits were set so that most buildings already met them. The law's own design makes 2030 the step that matters: the DOB describes stricter limits from 2030, aimed at a 40% cut in emissions from large buildings by 2030.
The penalty
Owners of buildings over their limit face an annual penalty of $268 per metric ton of CO2-equivalent above the limit, on top of penalties for failing to file.
Why electric chillers are a special case
Emissions are computed from each fuel a building uses, times a coefficient per unit. Two consequences for chiller plants:
- Electric chillers' emissions follow the grid. Every kWh a chiller plant saves reduces reported emissions by the grid-electricity coefficient. Steam-driven or gas-fired absorption chillers are counted on their fuel instead.
- RECs only offset electricity. From the reports filed in 2027, eligible renewable energy credits, tied to renewable resources that supply the NYC grid, may be used only to reduce emissions from grid electricity. An owner can, in principle, cover an electric chiller plant's emissions by buying RECs rather than making the plant more efficient. Fuel-side emissions such as boilers can't be offset that way.
So for many owners the business case for plant efficiency rests on the electricity bill and demand charges first, with LL97 as a second benefit. It is also a hedge against the cost of RECs and against rule changes. The same kWh saved lowers both.
Where plant efficiency moves the numbers
- Chiller kW/ton at part load, where most hours are spent: staging, chilled-water reset and condenser-water reset.
- Tower fan energy, which fouling and poor sequencing inflate (what fouling looks like in data).
- Standby operation: chillers and pumps running with little or no building load, often overnight. It is easy to find in trend data and often cheap to fix.
- Pumps, especially constant-speed ones running at full flow regardless of load.
Each of these shows up in a BMS export. Plant Check measures them from yours. To see what an efficiency gain is worth on the bill, try the chiller plant energy cost calculator.