Generators & Local Law 97 in NYC

The short answer: yes, generator fuel counts

Local Law 97 caps a building's total greenhouse-gas emissions — and that total includes every fuel burned on-site. A standby generator burns natural gas, diesel, or fuel oil, so whatever it consumes is converted into CO₂-equivalent and counted against your building's annual cap. The part that actually matters is how much it counts, and that comes down to three things: how the generator is used, what fuel it burns, and how often it runs — including required testing.

How Local Law 97 counts a generator

LL97 doesn't measure emissions from a tailpipe — it takes the fuel your building consumes and multiplies it by a per-fuel emissions coefficient to get CO₂-equivalent tonnes. Your generator's fuel use flows into that same calculation. Two levers move the number:

• How much fuel it burns — a function of the generator's size and its total annual runtime.
• Which fuel it burns — natural gas carries a lower coefficient than diesel or fuel oil, so fuel choice directly changes the tonnage.

Exceed your cap and the penalty has been $268 per metric ton of CO₂-equivalent over the limit, every year — which is why owners of larger buildings pay attention to every source, generators included.

Emergency standby vs. regular use — the distinction that decides the impact

This is the single most important factor, and it's where owners get surprised in both directions.

True emergency / standby generators — installed to carry life-safety and critical loads only during a utility outage, plus periodic testing — burn relatively little fuel over a year. For most buildings, their contribution to the LL97 cap is minor. A generator that runs a handful of hours during actual outages is not what pushes a building over its limit.

Generators used for regular operation — prime power, peak-shaving, or routinely running building loads to trim utility costs — are a completely different story. Run often enough, a large fossil-fuel generator can move a building meaningfully toward, or past, its cap. If anyone proposes a generator as a day-to-day power source, that runtime needs to be in the LL97 math before you commit.

Fuel type changes the number

Because LL97 applies a different coefficient to each fuel, the same amount of energy produces different reportable emissions depending on what you burn:

• Natural gas — the lowest coefficient of the common generator fuels, and the usual choice for permanent NYC standby units tied to the gas main.
• Diesel / fuel oil — heavier coefficients, so the same runtime reports more CO₂-equivalent. Often required where a code-compliant on-site fuel supply is needed for extended emergency operation.

Fuel choice is usually driven by code, runtime requirements, and what's available at the property — but it's worth knowing it also carries an LL97 consequence.

Don't forget the testing runtime

Here's the detail people miss: code-mandated exercise and load testing burns fuel that also counts. Emergency and standby systems are typically tested under load on a regular schedule — commonly monthly, per NFPA 110 and fire-code requirements. On a small residential unit that's negligible. On a large commercial generator, monthly load tests across a year add up to real fuel, and real reportable emissions. It's a small line item, but for a building sitting close to its cap, small line items matter.

Residential vs. commercial: who actually needs to worry

Single-family and small homes are, in almost every case, well under LL97's 25,000-square-foot threshold and aren't directly covered. If you're putting a standby generator on a house, LL97 isn't part of the conversation — sizing, fuel, and permitting are.

Larger multi-family buildings, co-ops, condos, and commercial properties over the threshold are where it matters. For these, an emergency standby generator is usually a minor contributor, but it still appears on the building's emissions report — and any proposal to use a generator for regular power should be checked against the cap first. Boards planning capital work should have their generator's fuel type and expected runtime accounted for alongside the rest of the building's electrification plan.

What building owners should do before installing

• Right-size the unit. An oversized generator burns more fuel per test cycle and per run-hour. Size to the loads that genuinely need backup, not the biggest box available.
• Pick fuel deliberately. Where code and runtime allow, natural gas generally reports lower than diesel or fuel oil.
• Keep emergency use separate from regular use. Hold the generator's role to genuine backup. If you're tempted to run it routinely to shave costs, model that runtime against your cap first.
• Consider battery storage. For some buildings, battery energy storage — charged off-peak — can cover short outages or peak-shaving with zero on-site combustion, keeping that load off your LL97 ledger.
• Document it accurately. Make sure the generator's fuel use and testing are captured correctly in your annual emissions filing — both under- and over-counting cause problems.

Where this fits the bigger LL97 picture

Local Law 97 pushes buildings toward electrification — heat pumps for heating and hot water, induction cooking, EV charging, and LED lighting under the companion Local Law 88. Backup-power planning fits naturally into that work: while you're upgrading service and panels for electrified loads, it's the right moment to plan clean, correctly-sized backup — whether that's a right-sized standby generator, battery storage, or a combination. That coordinated approach is squarely the electrical work we do.

How MP Electric NYC approaches it

We install residential and commercial standby generators across the five boroughs, to NYC code and NEC Articles 700/701/702 for emergency and standby systems. For buildings subject to LL97, we design backup power with the emissions picture in mind — right-sized units, sensible fuel selection, and coordination with your engineer of record, energy consultant, or board — and we handle the broader commercial electrical and electrification work that compliance usually involves. Tell us about the property and we'll put a clear plan and price in writing.