Read the manual thoroughly and understand all instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or visit www.generac.com with any questions or concerns.
- Always check local codes, as those will take precedence over these recommendations.
- Do not install a home standby generator under a wooden deck or platform.
- Units that do not feature the SwRI logo must be installed 5 ft. from combustible materials and 3 ft. from non-combustible materials.
- Consider possible carbon monoxide (CO) entry points beyond the required fire safety distances.
Home standby generator clearance requirements
Clearance requirements help ensure the generator operates at a safe distance where heat and fumes will not cause fires or health hazards. The exhaust gets extremely hot and remains hot after shutdown. Flammable materials may ignite and burn from the heat of the exhaust system.
Environment
This article applies to Generac residential standby generators, including:
- Air-cooled standby generators
- Liquid-cooled standby generators
Important: Reduced clearance distances based on testing by the Southwest Research Institute (SwRI) apply only to generator models marked with the SwRI logo. Generators without the SwRI logo must follow standard clearance requirements as specified in the installation manual and applicable codes.
Reference the installation manual
Refer to your generator’s installation manual for the most up-to-date information. Installation manuals can be found using the Generac.com product lookup page.
NFPA 37 overview
- The National Fire Protection Association’s standard for the installation and use of stationary generators.
- Its requirements limit the spacing of the generator from a structure or wall.
- The unit must be located where it is readily accessible for maintenance, repair, and first responders.
- Minimum clearance requirements are for adequate airflow, maintenance, and safety.
NFPA 37 requirements
For a complete and updated list, see the NFPA 37 web page.
- 5 ft. from openings in walls (operable windows, doors, vents, window wells, or other openings in the wall).
- 18 in. of clearance from the back of the generator to a stationary wall or building (based on testing by the Southwest Research Institute, SwRI).
- 5 ft. of clearance above the generator.
- 3 ft. of clearance at the front and both ends. This includes trees, shrubs, and bushes. Vegetation not in compliance could obstruct airflow, and exhaust fumes could inhibit plant growth.
- In addition to these requirements, ensure all potential sources of water intrusion are directed away from the generator enclosure: sprinklers, roof runoff, downspouts, and sump pump discharge.
Site selection and preparation
Important note: The diagram provided represents general guidelines and is not all-inclusive. A unit installed in accordance with NFPA requirements—including the offset reduction validated through testing by SwRI—may still allow CO to enter the structure. The unit may need to be installed farther from the structure than the NFPA requirements.
Potential CO entry points
Generator exhaust can enter a structure through large openings, such as windows and doors. However, exhaust and CO can also seep into the structure through smaller, less obvious openings.
Protect the structure
Verify the structure is correctly caulked and sealed to prevent air from leaking in or out. Voids, cracks, or openings around windows, doors, soffits, pipes, and vents can allow exhaust gas to be drawn into the structure. Examples of entry points are described in, but not limited to, the table shown in the installation manuals: How Do I Find a Copy of My Home Standby Generator Owner's Manual, Spec Sheets, or Installation Manual?
| ID | Entry point | Description / comments |
|---|
| A | Windows and doors | Architectural details that can be (or are) opened to admit fresh air into the structure, including inoperable windows or doors. |
| B | Garage door | CO can leak into the garage if the door is open or does not seal correctly when closed. |
| C | Attic vent | Attic vents, ridge vents, and soffit vents can admit generator exhaust. |
| D | Basement windows, crawl spaces | Windows, hatches, or crawl spaces allowing ventilation to or from the lower level of a structure. |
| E | Furnace intake / exhaust vent | Air intake and exhaust pipes for a furnace. |
| F | Wall cracks | Includes (but is not limited to) cracks in the wall or foundation, seepage holes in brick/mortar, degraded or damaged brick/mortar, or air gaps around doors, windows, and pipes. See Protect the structure. |
| G | Dryer vent | Exhaust duct for a clothes dryer. |
| H | Airflow restrictions | Structural features—including but not limited to corners, alcoves, fences, courtyards, and areas with heavy vegetation—can restrict proper airflow around the unit. Exhaust gases can collect in these areas. |
| J | HVAC components | Do not direct generator discharge into HVAC components, including but not limited to make-up air systems, AC condensers (which may blow exhaust gas into structure openings), and window AC units.
Important note: Mechanical and gravity outdoor air intake openings for HVAC supply air systems shall be located according to Section 401 in the ICC Mechanical Code. See the ICC Mechanical Code for any additional requirements. |
| K | CO detector | A permanently or semi-permanently mounted device that detects carbon monoxide (CO) within the living area(s) of the structure. |
What about other requirements and codes?
- Codes vary by region — Contact your local building inspection department. This department is typically reached through your city government’s website.
- Permitting varies by region — This includes the time frame to receive a permit, which permits must be pulled, and the associated costs. See What factors influence the cost of installing a home standby system?
- Plumbing and electrical — Generator installation involves plumbing and electrical work. This should be performed by experienced professionals. We recommend contacting a local certified dealer: How Can I Find a Generac Service Dealer in My Area?
Further information, such as the distance from the gas meter, can be found in the installation manuals. See the How Do I Find a Copy of My Home Standby Generator Owner's Manual, Spec Sheets, or Installation Manual? article for more information. Note that local codes should always be followed.
See also
