What Is Local Law 97?
Local Law 97 (LL97) is NYC's landmark building emissions law, enacted as part of the Climate Mobilization Act in 2019. It sets carbon intensity limits on buildings over 25,000 square feet — roughly 50,000 properties citywide — and imposes financial penalties on buildings that exceed those limits.
The law targets buildings because they account for approximately 70% of NYC's greenhouse gas emissions. Compliance is not optional, and the fine structure is designed to become progressively more difficult to ignore over time.
Which Buildings Are Covered?
LL97 applies to most buildings over 25,000 gross square feet in New York City. This includes:
- Residential buildings (condos, co-ops, rentals) above the threshold
- Commercial office buildings
- Mixed-use properties
- Hotels, hospitals, and institutions
There are limited exemptions — primarily houses of worship and certain affordable housing properties — but the vast majority of larger NYC buildings are subject to the law.
How Are LL97 Fines Actually Calculated?
This is where most building owners get lost. The fine is not a flat fee — it's calculated based on how far your building's carbon emissions exceed its specific limit, multiplied by your building's size.
Where Emissions = Sum of (Energy Use × Carbon Intensity Factor) ÷ Gross Floor Area
The carbon intensity limit is set per occupancy type — office buildings, residential buildings, and retail all have different thresholds. The $268 per tonne fine rate is fixed by the law for the current compliance period.
A Simple Example
Consider a 100,000 square foot mixed-use building with an emissions limit of 4.53 kg CO₂e/sf. If the building's actual emissions are 6.00 kg CO₂e/sf, the overage is 1.47 kg CO₂e/sf — or 147 tonnes CO₂e for the whole building. At $268/tonne, that's a $39,396 annual fine.
Key point: Fines are assessed annually. A building that does nothing faces the same fine every single year — and that fine grows significantly when limits tighten in 2030.
The Two Compliance Periods — And Why 2030 Matters More
LL97 operates in multi-year compliance periods, each with progressively stricter emissions limits:
| Period | Years | Limits | Fine Rate |
|---|---|---|---|
| Period 1 | 2024–2029 | Moderate — ~80% of buildings comply | $268/tonne |
| Period 2 | 2030–2034 | Strict — limits tighten by 40–80% | $268/tonne |
| Period 3+ | 2035+ | Near-zero carbon targets | TBD |
Period 1 limits were deliberately set to be achievable without major retrofits for most building types. Period 2 limits — which begin January 1, 2030 — are where the real challenge lies. Many buildings that are fully compliant today will face five-figure or six-figure annual fines starting in 2030 if they take no action.
That may sound far off. It isn't. Large-scale building retrofits — HVAC system replacements, electrification, envelope improvements — typically take 18 to 36 months from planning to completion. Buildings that wait until 2028 or 2029 to begin the process will struggle to complete work before fines begin.
What Drives a Building's Emissions Under LL97?
LL97 measures emissions based on energy consumption and the carbon intensity of each fuel source. Three factors drive most buildings' exposure:
1. Natural Gas Use
Steam heating, gas boilers, and gas hot water systems are the primary source of LL97 emissions for most NYC buildings. Natural gas carries a high carbon intensity factor under the law, meaning heavy gas users face disproportionate fines.
2. Electricity Grid Carbon Content
LL97 uses fixed carbon intensity factors for electricity — and those factors decrease over time as NYC's grid gets cleaner. This means that electrification becomes a more favorable strategy each year, even without changing a building's energy consumption.
3. Gross Floor Area
Fines scale directly with building size. A 500,000 square foot building that's 10% over its limit faces five times the fine of a 100,000 square foot building in the same situation.
What Can Building Owners Do Now?
The most important first step is understanding where your building actually stands. Many owners are surprised to find they're already compliant for Period 1 — or equally surprised to discover a significant Period 2 liability they weren't tracking.
Once you know your position, the path forward typically involves some combination of:
- Operational improvements — scheduling, controls, and maintenance changes that reduce energy use with minimal capital investment
- Equipment upgrades — replacing aging gas-fired equipment with higher-efficiency or electrified alternatives at end of life
- Electrification — transitioning heating and hot water systems from fossil fuels to heat pumps, which become cleaner as the grid decarbonizes
- Renewable energy credits (RECs) — a limited compliance pathway available for some building types in Period 1
- NYSERDA and Con Edison incentives — significant financial incentives exist that can materially reduce the cost of qualifying retrofits
The right strategy depends on your building's specific occupancy, systems, lease structure, and financial position. There is no universal answer — which is why independent technical advice matters.
Start with the data. Use our free LL97 calculator to look up your building by address and see your estimated emissions, compliance status, and projected fines for both Period 1 and Period 2. It takes under 60 seconds and requires no signup.
A Note on LL97 Reporting and Enforcement
LL97 compliance is self-reported — building owners file annual emissions intensity reports with the NYC Department of Buildings. The first reports covering 2024 emissions were due in May 2025. Penalties for non-filing are separate from (and in addition to) penalties for exceeding emissions limits.
The DOB is actively enforcing the law. Buildings that miss filings or misreport face significant additional penalties. If you haven't filed yet, addressing that is an immediate priority.
Know Where Your Building Stands
Our free LL97 calculator uses NYC open data to instantly show your building's emissions, compliance status, and estimated fines — no signup required.