Local Law 97 stopped being theoretical the moment 2024 ended. Period 1 limits are live, the first compliance reports are filed by May 1, and the math behind the 2030 step-down is starting to scare a lot of owners who quietly assumed they had time. This is a practical look at what LL97 means in 2026 — what is due now, what to plan for, and the mistakes I see owners make over and over.
A 90-second refresher
Local Law 97 caps the greenhouse gas emissions of buildings over 25,000 square feet in New York City. Each building is assigned an annual cap based on its occupancy types and floor area. If a building emits more than its cap, the owner pays a penalty of $268 per metric ton of CO2-equivalent over the limit, every year, until the building gets back under the line.
There are two cap periods most owners care about:
- Period 1: 2024 through 2029. Looser caps. About 11% of covered buildings are over.
- Period 2: 2030 through 2034. Caps drop sharply. Roughly 75% of covered buildings will be over without intervention.
Reports are filed annually with the NYC Department of Buildings. The 2025 report covering calendar year 2024 emissions was the first real one with teeth.
If you do nothing else this year, calendar your May 1 LL97 report deadline and confirm a Registered Design Professional has been engaged to certify it. The penalty for not filing at all — $0.50 per square foot per month — is often worse than the penalty for being slightly over your cap.
What is due this year
The May 1 LL97 report is the load-bearing item. To file it, you need:
- A full year of energy consumption data — the same data you used for your LL84 benchmarking submission, broken down by fuel.
- An emissions calculation that translates each fuel type into metric tons of CO2-equivalent using the coefficients in the LL97 rule.
- A certification by a Registered Design Professional (RDP) — typically a licensed PE or RA — submitted through the DOB NOW portal.
The report itself is not long. The work is in the inputs. If your benchmarking data is incomplete or your meter list is wrong, your LL97 numbers will be wrong, and you will be vouching for them under penalty of perjury.
Common Period 1 outcomes
Most owners fall into one of three buckets after running their 2024 numbers:
- Comfortably under cap. Great. File the report. Use the next four years to prepare for Period 2 — don't coast.
- Slightly over cap. Calculate the penalty exposure. For a building 5% over, this is often a few thousand dollars per year. Compare that against the cost of the obvious efficiency moves (controls tuning, lighting upgrades, low-flow domestic hot water) before assuming you need a capital project.
- Significantly over cap. This usually means an older heating plant, electric resistance heat, or a fuel mix dominated by #4 oil. You need a plan, not a panic. Engage an energy professional and start mapping a Period 2 strategy now.
Pitfalls I see all the time
After helping owners run LL97 numbers on dozens of properties, the same mistakes keep showing up.
Treating the cap as the deadline
The cap is the cap. The deadline is May 1. Owners conflate them and end up scrambling in April to optimize emissions for a year that already ended in December. You cannot retroactively reduce 2025 emissions. What you can do is file accurately, pay the penalty if applicable, and start working on the next reporting year.
Wrong building classification
Your cap depends on the occupancy types in your building. A mixed-use building with ground-floor retail, a parking garage, and residential floors above has three different cap coefficients applied to three different floor areas. Owners frequently submit using the dominant occupancy only and end up with the wrong cap — sometimes harshly so. The PLUTO data is a starting point, not the truth. Verify against the Certificate of Occupancy.
Ignoring the GHG coefficients
LL97 uses specific emissions factors for each fuel. Natural gas, fuel oil #2, fuel oil #4, district steam, and grid electricity all have different multipliers. Some — notably the grid electricity coefficient — are scheduled to drop over time as the grid decarbonizes. A building that looks dirty in 2026 may look much cleaner in 2030 just from grid changes. That doesn't mean ignore it; it means model the trajectory honestly before making capital decisions.
Forgetting tenant-controlled spaces
Net-leased commercial tenants often pay their own energy bills and the owner never sees the data. LL97 doesn't care. The whole-building emissions count toward the cap. If you have triple-net tenants, you need a data-sharing arrangement — whether through Con Ed's Aggregated Whole-Building data or a tenant amendment — before you can even file.
Skipping the good-faith efforts pathway
If you can show that you are actively decarbonizing, the rule allows for adjusted penalties in some circumstances — particularly if you have filed an electrification plan or have an approved decarbonization study underway. This is not a get-out-of-jail card, but it is worth knowing about for buildings with serious Period 2 exposure.
The Period 2 cliff
Here is the part that keeps owners up at night. The 2030 caps are not a polite step down. For most building types they are roughly half of the Period 1 cap. A building that is 10% under its 2024 cap might be 60% over its 2030 cap.
Why does this matter in 2026? Because the lead time on serious decarbonization work is long.
- A heat pump conversion in a Class B office building can take 18 to 30 months from feasibility study to commissioning.
- A windows package in a pre-war multifamily building can take three years if you are working occupied units.
- A ConEd service upgrade — required for most fuel switching — has a queue measured in years right now.
If you start the design work in 2026, you are commissioning in 2028, ramping in 2029, and just barely in time for 2030. If you start in 2028, you are not making it.
The owners who will sail through Period 2 are not the ones with the fanciest tech. They are the ones who started the boring work — meter cleanup, controls audits, electrification feasibility — three or four years before the deadline.
What to do this quarter
If your portfolio includes any building over 25,000 square feet, here is a reasonable order of operations for the next 90 days:
- Confirm your covered buildings list. Every building over 25,000 sf in NYC. Don't forget condos and co-ops where the board may not realize they are covered.
- Reconcile benchmarking and LL97 data. Same fuels, same square footage, same year. Discrepancies between your LL84 and LL97 filings are an audit flag.
- Engage your RDP early. Good ones are booked solid in April. If you wait until mid-April you will be at the back of the queue.
- Run your Period 2 model. Ask your engineer to project 2030 emissions under the current operating profile. The number will tell you whether you have a tuning problem or a capital problem.
- Document everything. Save the bills, save the certifications, save the calculations. If DOB audits you in 2027, you will be glad you did.
If you are managing a portfolio and your LL97 spreadsheet is starting to feel like a liability, LLDesk maps every covered building automatically and tracks the May 1 deadline and the supporting documents alongside the rest of your compliance calendar.
Key takeaways
- Period 1 is real. The May 1 LL97 report is the immediate priority and requires a Registered Design Professional certification.
- The penalty for not filing is often worse than the penalty for being over cap. File something, even if the news is bad.
- Common errors — wrong occupancy mix, missing tenant data, conflating LL84 and LL97 inputs — get caught in audits.
- Period 2 caps in 2030 are roughly half of Period 1 for most building types. The lead time on real decarbonization is 2 to 4 years.
- Start the boring work now: meter cleanup, controls tuning, fuel switching feasibility. The owners who win Period 2 started in 2026.