Keep a portable generator at least 20 feet from your house, with the exhaust pointed away from windows, doors and vents. That’s the Consumer Product Safety Commission’s rule. Never run one in a garage, basement, shed or carport, even with the door open. Home standby generators are different: they’re built and listed to sit closer, typically 18 inches from the wall and at least 5 feet from any window, door or vent, per Generac’s installation guidelines and the NFPA 37 standard.
Portable generators: 20 feet, exhaust pointed away
The CPSC’s 2026 hurricane season warning says to run portable generators outside only, “at least 20 feet from homes and buildings, with exhaust directed away from windows, doors and vents.” It also says never to use one inside a home, garage, basement, crawlspace, shed or other enclosed area, even with doors or windows open. Generators are one of the leading causes of carbon monoxide deaths after storms.
Twenty feet is a minimum, not a guarantee. On a still day, CO can drift toward the house, so:
- Point the exhaust away from the house and from your neighbors’ homes.
- Keep the generator away from open windows, including the neighbors’.
- Put battery-powered or battery-backup CO alarms on every level of your home and outside sleeping areas, and test them monthly.
- Don’t put the generator under a deck, porch roof or tarp lean-to against the house. If you need rain protection, use a generator tent or cover made for that model that keeps it fully in the open.
A 25- to 50-foot heavy-duty cord makes the distance easy. Ace Hardware carries generator cords in lengths up to 100 feet. (We may earn a commission if you buy through this link.) For running power into the house, use a transfer switch or interlock, never a wall outlet: here’s how to hook up a generator to your house.
Generator extension cord gauge calculator
A longer cord means a safer distance, but a cord that’s too thin for the length and load overheats and drops voltage, which is hard on motors and electronics. Pick your cord type, enter the running watts you’ll plug in, and choose the length. The lower the gauge number, the thicker the wire.
How it works: amp ratings are the National Electrical Code limits for flexible cords (Table 400.5(A)(1)), and voltage drop uses stranded copper resistance from NEC Chapter 9, Table 8. “Good” keeps the drop under 3%; 3 to 5% is acceptable. Never use a cord rated for less than your load, and use outdoor-rated, heavy-duty cords only.
Home standby generators: Generac’s clearance rules
Permanently installed standby generators are designed with enclosures and exhaust systems that let them sit near the house. Generac’s clearance guidelines, based on NFPA 37, call for:
| Clearance | Minimum |
|---|---|
| Back of unit to the house wall | 18 inches (models with the SwRI logo) |
| Windows, doors, vents and other openings | 5 feet |
| Above the unit | 5 feet |
| Front and both ends (including shrubs) | 3 feet |
| Older units without the SwRI logo | 5 feet from combustible materials, 3 feet from non-combustible |
Generac notes that local codes take precedence and that exhaust can still reach the house in some conditions, so the unit may need to go farther away. Other brands publish their own clearances in their installation manuals. Most towns also require a permit for a standby generator, and some set their own setbacks from property lines, so check with your building department before you pick a spot.
How far should a generator be from an RV or camper?
Treat your RV like a house: keep a portable generator as far from it as your campsite allows, ideally 20 feet, with the exhaust pointed away from your RV and your neighbors’ rigs. Keep windows on that side closed, and make sure your RV’s CO alarm works. Many campgrounds also have generator quiet hours. With a built-in RV generator, check that the exhaust pipe isn’t damaged or blocked by snow, a wall or tall grass, since a blocked exhaust can push CO under the RV. See how to extend a generator exhaust safely.
Related guides: Best Generators for Hurricane Season, Stolen Generator and Portable Generator Shelters. Also see: Generator power inlet box.
FAQ
Can I run a generator in my garage with the door open?
No. The CPSC specifically warns never to run a generator in a garage, even with the door open. CO builds up quickly and can seep into the house.
Can I put a generator on my porch or under a carport?
No. A porch or carport traps exhaust next to the house. Keep it in the open, 20 feet away.
How close can a Generac standby generator be to a window?
At least 5 feet from any operable window, door or vent, according to Generac’s installation guidelines.
Does the distance rule apply to inverter generators?
Yes. Inverter generators produce less noise but still make deadly carbon monoxide. Follow the same 20-foot rule. More tips: portable generator safety.
What gauge extension cord do I need for a generator?
It depends on the load and the length. For a typical 120 V load around 12 to 13 amps (about 1,500 watts), a 12-gauge cord works up to about 50 feet and a 10-gauge cord up to about 100 feet with less than 3% voltage drop. Use the calculator above for your own numbers.