Keep a Portable Generac 20 Feet Away; Standby Clearances Differ
Place a portable Generac at least 20 feet from the house. For a standby Generac, follow model-specific wall, opening and service clearances.
Place a portable Generac generator outdoors at least 20 feet from the house, with its exhaust pointed away from the home and nearby buildings. A permanently installed Generac standby generator follows different, model-specific clearances: some approved units may sit 18 inches from a wall, but they still generally need at least 5 feet from doors, windows, vents and other wall openings.
| Generac type | Placement threshold |
|---|---|
| Portable generator | At least 20 feet from the house |
| Standby generator with qualifying SwRI marking | Back may be 18 inches from a stationary wall, subject to its manual and local code |
| Standby generator near an opening | At least 5 feet from windows, doors, vents, window wells and other wall openings |
| Standby generator front and ends | 3 feet of clear space |
| Above a standby generator | 5 feet of clear space |
Portable Generac: use the 20-foot rule
The U.S. Consumer Product Safety Commission says to operate a portable generator outside, at least 20 feet from the house. A porch or carport is still too close. Point the exhaust away from the home and other buildings, and close nearby windows and vents in the exhaust path (CPSC, 2026).
Do not run it in a garage, basement, crawlspace or shed—even with doors and windows open. Generac’s GP Series manual likewise says partly enclosed spaces are unsafe, requires outdoor operation far from openings and calls for 5 feet of clear space on every side to reduce overheating and fire risk (Generac GP Series owner’s manual). The 5-foot equipment clearance does not replace CPSC’s 20-foot house separation.
If the only available spot is inside or closer than 20 feet, do not start the portable generator there. A shed is suitable for storage while the machine is off, not ordinary operation; see whether a generator can run or be stored in a shed.
Standby Generac: 18 inches is conditional, not a universal answer
For Generac residential standby models bearing the applicable Southwest Research Institute (SwRI) marking, Generac permits 18 inches between the back of the unit and a stationary wall. It also lists 5 feet from wall openings, 3 feet at the front and both ends, and 5 feet above. Units without that marking require 5 feet from combustible material and 3 feet from noncombustible material unless their installation instructions specify otherwise (Generac clearance guidance).
Those dimensions are minimum clearances, not proof that every 18-inch location is safe. Exhaust can enter through soffits, attic vents, foundation cracks, dryer vents, HVAC intakes and garages. Corners, fences and dense vegetation can also trap exhaust. Generac says a site may therefore need greater separation even when the stated minimums are met.
There is no universal maximum distance for a standby generator. A longer placement may work if the fuel piping, power conductors and control wiring are correctly designed for the run (Generac distance guidance).
Use the installation manual for the exact model and have the location approved under local building, fire, fuel-gas and electrical requirements. Standby installation involves both fuel and electrical work, so placement should be confirmed by the installer and local permitting authority before the pad and lines are built.
Keep working battery-backed carbon-monoxide alarms on every level and outside sleeping areas. If an alarm sounds—or anyone becomes dizzy, weak or nauseated—go outside immediately and call 911.