Emergency Generators

Fact Sheet on Emergency Backup Generators

Do Emergency Backup Generators require a permit from the South Coast AQMD?

All internal combustion engines (ICEs) greater than 50 brake horsepower (bhp) and gas turbines greater than 2,975,000 British thermal units (Btu) per hour are required to obtain a permit to construct from the South Coast AQMD prior to installation of the engines at a site. 

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What are the air emissions from backup generators?

Most of the existing emergency backup generators use diesel as fuel.  Emissions of Nitrogen Oxides (NOx) from diesel-fired emergency engines are 200 to 600 times greater, per unit of electricity produced, than new or controlled existing central power plants fired on natural gas.  Diesel-fired engines also produce significantly greater amounts of fine particulates and toxics emissions compared to natural gas fired equipment.  NOx is a primary component of smog.  Engines operated on fuels other than diesel, such as natural gas, ethanol, propane or with dual fuels (diesel only for initial start-up and then primarily natural gas) are much cleaner and produce significantly less air pollution for the same amount of energy produced.  

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What is considered an emergency backup generator by the South Coast AQMD?

A standby ICE or turbine for non-utility power generation that does not operate more than 200 hours a year and is only operated in the event of an emergency power failure or for routine testing and maintenance is considered an emergency backup generator for power generation.  

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Can these engines be operated during periods of threatened power blackouts and are the hours accumulated towards the 200 hours?

ICEs for emergency power generation that are fired on natural gas only, and are permitted by the South Coast AQMD may be operated during Stage II or Stage III electrical emergencies declared by the Independent System Operator (ISO) and during actual or imminent blackouts.  The hours the engines are operated during these periods in any one year are accumulated toward the total 200 hours.

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What actions should be taken if the backup generation equipment operation will exceed the 200 hours limit?

Operating the equipment in exceedance of the permit condition limit of 200 hours is a violation and may result in a notice of violation and a fine.  To avoid the possibility of a violation, the operator should petition the South Coast AQMD's Hearing Board for a variance to operate in excess of the allowed 200 hours before it is anticipated that the hours may be exceeded

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Will the Hearing Board grant the variance and for how many additional hours?  Also, do we need a lawyer to represent us at this variance hearing?

There is no guarantee that the Hearing Board will grant or deny a variance.  Each variance is evaluated on a case-by-case basis, to evaluate emissions impacts, mitigations and other factors. While it is not necessary, it may be prudent to hire an attorney or a consultant to prepare and present the case and make the necessary findings before the Hearing Board.  You may contact the Hearing Board office at (909) 396-2500 for further information and for the variance application package. See the Hearing Board and variances page for additional information.

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What are the different options for obtaining a permit for an emergency backup generator and what are the permit requirements for each of the options?

The different options are to:

a. Rent an engine permitted by the South Coast AQMD
The permits that have been issued to the rental yards are "Various Location Permits" and allow the operation of the engines at different locations as long the specific permit conditions listed on the permits are met.  You do not have to obtain a separate permit to operate this equipment at your facility; however you may be responsible for reporting emissions from rental equipment to the South Coast AQMD. 

b. Purchase or lease an engine that has been certified by the South Coast AQMD.

The South Coast AQMD has certified certain models/families of equipment as meeting all applicable air quality requirements and have issued permits to the dealer/distributor of these engines.  If you have purchased or plan to purchase equipment from a manufacturer participating in the program, be sure to pick up your application package from the dealer/distributor.  A list of dealers/distributors (XLS, 79 kb, Last Updated 12/15/2023) that are participating in this program is available on South Coast AQMD's website. 

You will have to submit an application for a Permit to Construct/Operate this certified engine and pay the reduced permit processing fee.  These applications are issued in an expedited manner.

c. Purchase or lease an engine that will meet South Coast AQMD's BACT requirements. 
If you plan to purchase a new or used engine from a manufacturer/dealer or from a third-party, you will have to submit a permit application and appropriate fees to obtain a Permit to Construct/Operate before installing the engine at your site.  The internal combustion engines must meet South Coast AQMD's Best Available Control Technology (BACT) requirements.  BACT for diesel fired emergency back-up engines or for natural gas fired emergency back-up engines can be found at BACT Guidelines for Non-Major Polluting Facilities . 

d. Rent an engine that has been certified by the California Air Resources Board (CARB).

CARB has a similar but statewide program to certify backup generation engines.  The use of these CARB certified engines does not require a permit from the South Coast AQMD; however, these statewide registered portable generators are not to be operated during ISO Stage II or Stage III alerts, unlike the units permitted by the South Coast AQMD.  They can only be used for emergency power generation during actual or imminent blackouts.


Additional information about the Statewide Portable Registration Program is available on the California Air Resources website at   

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Is it possible to permit natural gas fired engines for more than 200 hours a year of operation? 

Yes, it is possible to obtain a permit for these engines for more hours provided it complies with the requirements of Regulation XIII (modeling, offsets, BACT) and Regulation XIV (New Source Review for Toxics).  These applications are handled on a case-by-case basis and the increased hours of operation granted will also vary based on the site specific location.   

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Can I update my permit condition to increase the hours of operation to 200 hours a year if I have an existing condition for the emergency ICE for power generation with lower hours (less than 200 hours/year)?  What is the procedure to modify the conditions? 

Yes, applications submitted by an emergency standby generator operator to revise the current permit condition to increase the allowed hours to the annual maximum of 200 hours as specified in South Coast AQMD's Rule 1110.2 can be approved.   However, testing and maintenance hours are limited, in most cases, to 20 - 50 hours annually pursuant to Rule 1470. 

To request the change of permit conditions, you must submit Form 400-A, a copy of the previous permit, and the permit processing fee.  The application to modify the conditions on the permit will be treated as an Administrative Change in Permit Conditions thereby qualifying for a reduced fee.

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What are micro-turbines and what are the permit requirements for these? 

A typical micro-turbine power generation system is about the size of a refrigerator and generates 30 kilowatts of electricity.  There are larger units that generate 60 kilowatts of electricity.  These are modular units that can be combined to generate more power.  The micro-turbines are normally operated on gaseous fuel (natural gas, propane or digester gas) and have much lower emissions than diesel fired engines; however, permits are required if the micro-turbines are fired on landfill gas, regardless of the size.  Permits are not required for the micro-turbines if the total combined rating is less than 2,975,000 British thermal units (Btu) per hour.  

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What is the permit application process? 

It is advisable before purchasing any equipment to consult with the South Coast AQMD and apply for approval of a Permit to Construct from the South Coast AQMD to install the engine on your site.  Typically, the South Coast AQMD either issues a Permit to Construct or a Permit to Construct/Operate.  To obtain a permit, a permit application must be submitted together with the correct permit-processing fee.  The application package should consist of Form 400-A (PDF), Form 400-PS (PDF), Form 400-CEQA (PDF) and Form 400-E-13a (PDF).  The forms required for the Registered/Certified engines are Form 400A, Form 400 CEQA and End-User Form for Emergency Generator (Form EIC-RE) (Last Updated 7/1/2022) (PDF, 94kb)

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Can I receive an expedited permit from the South Coast AQMD? 

The South Coast AQMD generally processes a new application for a Permit to Construct for a backup generator in 2 to 3 months depending on engineering workload or the complexity of the project.  However, the South Coast AQMD permitting staff can work on an overtime basis, if requested by the applicant, to process the permits in a more expedited manner.  These applications are subject to additional fees as specified in Rule 301(v) and will also depend on staff availability to work on overtime.  To request expedited processing, please submit Form 400-XPP (PDF) together with the application package.

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 What are the permit processing fees for the various permit applications?

Type of equipment

Fee Schedule

Internal Combustion (IC) Engine, Emergency, 51-500 HP


Internal Combustion (IC) Engine, Emergency, >500 HP


Internal Combustion (IC) Engine, non-emergency, 50-500 HP


Internal Combustion (IC) Engine, non-emergency, >500 HP


Certified ICE

50% of A

Administrative change of conditions


Gas turbines, landfill/digester gas , <0.3 MW


There is a discount of 50% of the permit processing fee for small businesses (less than 10 employees and with gross income less than $500,000) and a higher fee of 150% of the permit processing fee for equipment installed and operated without a permit.

* New fees go into effect July 1 of each year.  Please consult current version of Rule 301 for the latest fee information.

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Additional Information:

  • Check South Coast AQMD's website at for news releases, Executive Orders, and Permit information and forms.

  • South Coast AQMD Permit Application forms

  • Permitting of Certified Registered engines: Susan Tsai at 909-396-2529 or CJ Chang at 909-396-3293

  • Permitting of emergency backup generators: Emergency IC Engine Hotline at 909-396-3396.

  • South Coast AQMD General Number: 909-396-2000

  • South Coast AQMD Complaint Line: 1 800-CUT-SMOG (288-7664)

  • California Air Resources Board: to external website.

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