How Far Should a Generator Be From the House?

The power went out two hours ago and the freezer is warming up. You pull the portable generator out of the shed, set it on the driveway about eight feet from the back door, and run a cord through a cracked window. By midnight the house smells normal, everyone is asleep — and carbon monoxide is quietly entering through that cracked window, the dryer vent, and a gap under the garage door. This scenario is not rare: portable generators are one of the leading sources of fatal CO poisoning in the United States, and "too close to the house" is the common thread. This page covers the recommended safe distance, a practical placement checklist, and the most common mistakes that still cause tragedies.

This is general safety information — not medical advice. If a CO alarm sounds or you suspect exposure, move to fresh air and contact emergency services.

In 60 Seconds

Run portable generators outdoors only — never inside a home, garage, basement, shed, or crawlspace.
Place the generator at least 20 feet (about 6 meters) from doors, windows, and vents — farther if wind or terrain funnels exhaust toward the building.
Point the exhaust away from the house and neighboring homes.
"20 feet away" can still be dangerous if the generator sits in a courtyard, under a deck, or near an HVAC intake.
Ensure CO alarms are working and have fresh sensors — especially during outages when generator use peaks.

Why Distance Matters

Generators produce carbon monoxide in their exhaust. CO is invisible and odorless, so you cannot rely on smell to tell whether fumes are entering your home. Even small exhaust infiltration can build up indoors, especially overnight when doors and windows are closed. The goal of distance rules is to keep exhaust dilution high and prevent the plume from re-entering the structure through openings or HVAC intakes.

The "20-Feet Rule" — and Why It Is a Minimum

A widely cited safety baseline is at least 20 feet from doors, windows, and vents. This distance comes from CPSC guidance and is meant to reduce the chance of exhaust drifting back into the home. However, distance alone is not the whole story. "20 feet away" can still be dangerous if:

The generator is aimed toward an open window.
It sits in a courtyard or between buildings that trap fumes.
It is placed below a window well or near a basement entry where air can pool.
Wind pushes the exhaust plume directly toward the house.

Treat 20 feet as the starting point, not the finish line. Adjust based on your specific layout.

Placement Checklist

Rule	Why It Matters
Outdoors only — never in a home, basement, crawlspace, shed, or garage	Even "with the door open" traps enough CO to be fatal
≥20 feet from doors, windows, and vents	Reduces exhaust re-entry through openings
Exhaust pointed away from the building	Prevents plume from drifting toward doors or intakes
Avoid low spots, window wells, enclosed patios, and under-deck areas	CO can pool in sheltered or recessed spaces
Keep the generator dry with a purpose-built canopy	Never drape a tarp over a running unit — fire and CO risk
Use heavy-duty outdoor extension cords or a transfer switch	Reduces temptation to place the generator closer for shorter cord runs

Common "Almost Outside" Mistakes That Still Cause CO Poisoning

Many CO incidents happen when the generator is "basically outside" but still in a partially enclosed or airflow-trapping area. These setups can funnel exhaust straight into living spaces:

In a garage with the door open — still dangerous. See can you run a generator in a garage with the door open.
On a covered porch or screened-in patio — roof and walls trap exhaust.
Under a deck, especially near a basement door or dryer vent outlet.
Next to a window A/C unit or near a fresh-air HVAC intake.
In an enclosed courtyard between buildings where air recirculates.

How to Verify Your Placement Is Safer

Stand where people sleep and look for direct airflow paths from the generator location to bedroom windows and vents.
Check wind direction periodically — storms can shift wind and push exhaust toward the house.
If you use a portable CO monitor, place it near sleeping areas as an extra layer (not a replacement for installed alarms).
Ensure working CO alarms are installed on every level and not expired.

Transfer Switches: Reduce CO Risk by Design

The safest "distance" is achieved when you do not need to drag cords toward the house. For homes with frequent outages, a licensed electrician can install a transfer switch or interlock that lets you keep the generator in a consistent safe spot and connect power correctly. This also eliminates the common temptation to run a generator closer just because extension cords do not reach.

A transfer switch also prevents backfeeding — sending power back into utility lines — which is a separate electrical hazard. If a full transfer switch is not practical, a manual interlock on the main panel is a simpler alternative that still lets you place the generator at a safe distance and route power through the panel instead of through extension cords snaked through windows.

CO Alarms During Outages

Power outages are exactly when people run generators and use alternative heat — which increases CO risk. Make sure at least one alarm near sleeping areas runs on batteries or battery backup. If your alarms are hardwired without backup, they go silent during the outage when you need them most. For coverage planning, see how many CO detectors do I need.

Before storm season, test every CO alarm in the house and replace any unit that is past its end-of-life date. Consider adding a battery-powered alarm near the entry closest to your usual generator placement as an extra early-warning layer.

Frequently Asked Questions

Is 10 feet enough if I aim the exhaust away from the house?

No. Ten feet is commonly too close, especially near windows, vents, or a garage. Treat 20 feet as a minimum starting point and increase it if the layout or wind could push exhaust back toward the house.

Can I run a generator on a porch or under a patio roof?

Avoid it. Covered or semi-enclosed spaces can trap and redirect exhaust. Generators should be in open air with plenty of clearance in all directions.

Does wind direction change the safe distance?

Yes. Wind, walls, and terrain can channel exhaust toward openings. If wind pushes fumes toward the house, move the unit farther and reposition the exhaust direction.

Can generator exhaust enter through attic vents or soffit openings?

Yes. Soffit vents, ridge vents, and gable vents are all potential entry points. Position the generator away from these openings and point the exhaust in the opposite direction.

Should I put a CO detector near the door closest to the generator?

It is a good extra layer. Place a CO alarm inside the home near the entry closest to where you run the generator, and make sure sleeping-area alarms are working and not expired.

Sources & References

Published: January 15, 2024