How Far Should a Generator Be From the House? The 20 Foot Rule Explained

A portable generator stands outdoors, at least 20 feet from the house, with its exhaust pointed away from every door, window and vent. The exhaust carries carbon monoxide, a gas you cannot see or smell, and distance plus direction lower the chance that it reaches your rooms. On my land every engine has a place where its exhaust is allowed to go, and for a generator that place is far from the house. Below I give the distances the CPSC, the CDC and the makers state, show where they differ, and walk through how I pick the spot.

How Far Should a Generator Be From the House? The Short Answer

Put the generator at least 20 feet from the house and aim the exhaust away from it. The CPSC says to operate generators outdoors only, at least 20 feet from homes and buildings, with the exhaust directed away from windows, doors and vents. The CDC gives the same 20 feet, measured from windows, doors and vents.

Three more rules travel with the distance. Run the generator outdoors only, never in a garage, basement, crawlspace, shed, carport or on a porch, even with the doors open. Keep battery-powered CO alarms on every level of the house and outside the sleeping areas. Read the manual too, because it adds clearances of its own.

I walk the distance off in daylight before I set up, because a spot that looks far from the house at dusk is often closer than I think. A tape measure settles it in a minute.

What the CPSC, the CDC and the Makers Say

Three groups give a distance, and their numbers are not the same. The table puts them side by side, each as its source states it.

Where the Agencies Agree and Where They Differ

The CPSC and the CDC agree on 20 feet. They word it differently: the CPSC measures from the house and other buildings, the CDC from windows, doors and vents, and one CDC page says “more than” 20 feet. Measure from the nearest wall, door, window and vent, and add a few feet if the yard allows. That one habit meets every version of the wording. If no spot on your property is 20 feet from your house, other buildings and their doors, windows and vents, do not run a portable fuel generator there, and do not fall back to the manual’s smaller clearance.

Why the Makers’ Numbers Are Smaller

The manuals list 3 to 5 feet, a fraction of the agency figure. According to Honda, the muffler stays hot after the engine stops, and its 3 feet sits next to that warning. The other manuals list their distances as clearance around a running engine.

Where an agency and a maker differ, follow the stricter one. That is the agency distance every time, and the manual’s clearances still apply on top of it.

Why Distance Alone Is Not Enough

Distance thins the exhaust, and direction lowers the chance that it reaches an opening. You need both, plus a warning system inside the house for the day one of them fails.

Point the Exhaust Away From Every Opening

Aim the exhaust away from the house and from every door, window and vent. The CPSC also says to close windows and seal vent openings that sit near the generator or in the path of its exhaust. A CDC and Florida health department analysis after four hurricanes in 2004 found that generators placed indoors, in garages or outdoors near windows caused nearly all of the CO exposures among 167 treated people (1).

I turn the exhaust toward the open orchard rows, so the exhaust is aimed away from the house and the sheds. I also keep the windows on that side of the house shut while it runs.

A CO Shutoff Is a Backup, Not a Permit

The CPSC recommends buying a model with a carbon monoxide shut-off feature. It shuts the engine off when dangerous CO levels build up around the generator, and models certified to the PGMA G300-2023 and UL 2201-2023 standards carry CO safety technologies. A shutoff is a second line of defense. It never makes a closer spot acceptable, so the 20 feet stays. I show how one such shutoff works on a three-fuel unit in my review of the Westinghouse WGen9500TFc.

Where a Generator Must Never Run

A distance rule assumes open air. Enclosed and half-enclosed spaces break that assumption, and the records from real outages show how often it happens.

• Garage: never, with the door open or shut.
• Basement or crawlspace: never, with a window or hatch open or shut.
• Shed: never, whatever the size of the shed.
• Carport or porch: never. The CPSC says a generator on a porch or in a carport is too close to the home.
• Deck beside the house: no, because the deck sits inside the 20 feet.

What the Garage Tests Show

NIST ran portable gasoline generators in an attached garage of a test house for the CPSC. Across seven door and ventilation setups, peak CO in the house ran from under 10 parts per million to over 10,000 (2). The highest level came with the garage bay door closed and the door into the house open a crack. The lowest came from a prototype with CO emission controls, the bay door open and the house door closed, and the unmodified generator in the test had none.

That is why the agencies say never, even with the door open. The best reading came from an experimental low-emission prototype, not from the unmodified generator.

What Happens in Real Outages

After a major ice storm in Maine, researchers counted 100 CO poisonings in 42 incidents. The strongest risk factor was putting the generator in a basement or an attached structure such as a garage (3). In Kentucky in 2009, ten people died of CO poisoning in two weeks, and eight of those deaths were tied to where a generator stood (4). A Seattle series of 37 generator incidents found 29 in the home environment, most often the garage, with lack of awareness of the danger the most common reason (5).

When a neighbor asks about running a generator in a shed or a garage, my answer is always the same: it never goes inside. That answer costs nothing, and it is the one the outage records back.

How to Pick the Spot, Step by Step

This is the order I follow every time. Each step comes from the agency guidance or the maker’s manual, and none of them takes long.

1. Find open, flat ground at least 20 feet from the nearest wall, door, window and vent of the house, and from other buildings.
2. Measure it with a tape measure. Pacing is too loose for a safety distance.
3. Set the generator on a level, hard surface with open air around it, and keep the clearance the manual lists.
4. Aim the exhaust away from the house and from every opening, including a neighbor’s.
5. Close windows and seal vents that sit near the generator or in the path of its exhaust.
6. Check that the battery CO alarms in the house work before you start.
7. Plug appliances in with a grounded, outdoor-rated extension cord, using the cord size and length the manual’s chart gives. For the house itself, my guide on connecting a generator safely covers cords, transfer switches and interlocks.
8. Stop the engine and let it cool before you add fuel, and refuel outdoors.

Here is a worked example. A gravel pad sits 12 feet from the back wall. That meets a 5-foot manual clearance more than twice over, and it still falls 8 feet short of the 20-foot rule. The pad has to move. On my farm yard the gravel pad has room to spare, so the 20 feet costs me a longer cord and nothing else.

Never connect the generator to a wall outlet to feed the house, as my guide on plugging into a wall outlet explains. That can send power back into the utility line and kill line workers. House wiring takes a transfer switch or an interlock fitted by a licensed electrician.

Wind, Storms and Wet Weather

I set the generator so the wind carries the exhaust away from the house, but the 20 feet stays whatever the wind does. In rain or snow, keep it dry only as the manual allows, with a listed cover or canopy that leaves the exhaust open, as I explain in my guide on generator use in the rain, and never touch it with wet hands or while standing in water. A closed tent or box around a running engine is another enclosed space.

Standby Generators

A permanently installed standby generator is a different job. Its maker’s installation instructions and local code set the distance, and a licensed installer does the placement. This article covers portable units only. My guide to the generator transfer switch explains manual and automatic switches, plus interlocks and inlet boxes.

Carbon Monoxide Alarms Inside the House

Distance and direction lower the risk, and an alarm warns you when something goes wrong anyway. The CPSC says to install working CO alarms, battery-operated or with battery backup, on every level of the home and outside sleeping areas. The CDC asks for alarms near every sleeping area. Test them monthly and replace the batteries when needed. I test every alarm in the house on the day I check the generator’s oil so the checks stay together, while my guide on how often to change oil covers the generator’s oil-change schedule.

The numbers show why. An ice storm cut power to most households in Mecklenburg County, North Carolina, in 2002. In the next nine days 124 people developed symptomatic CO poisoning, and 96.2% of the severe cases were in homes with no reported working CO alarm (6). The county then required battery backup alarms in all residences.

Keeping the Fumes Outside

Remember three things. Stand the generator at least 20 feet out with the exhaust turned away, keep it out of every garage, shed, carport and porch, and keep working battery alarms inside. If you are still choosing a unit for outages, my home backup generator picks compare nine options.

My own tip: I mark the spot once with a stake at 20 feet, so I never guess the distance in the dark. If your yard has no spot that meets the distance, do not run the generator there. Use a different power source instead, such as one of the portable power station picks in my roundup, which make no exhaust. Next, read the placement page of your manual and test your CO alarms this week. A generator 20 feet out with its exhaust turned away lowers the chance of fumes reaching the house, and the alarms inside cover the rest.

Frequently Asked Questions

Where do you put a generator during a storm?

Put a generator during a storm outdoors on open, level ground at least 20 feet from the house, with the exhaust pointed away from doors, windows and vents. Keep it dry only in the ways the manual allows, such as a cover or canopy that leaves the exhaust open, and never run it in a garage, shed or on a porch.

Are generators safe to use?

Generators are safe to use when you follow the placement and electrical rules, and dangerous when you do not. Run the generator outdoors at least 20 feet from the house, keep working battery CO alarms inside, and plug appliances in with a grounded outdoor-rated cord, never into a wall outlet.

Is it okay to run a generator on a deck?

Running a generator on a deck is not okay, because a deck beside the house sits inside the 20 feet the CPSC requires. The CPSC also says not to run one on a porch or in a carport, so move it to open ground and run a cord to it.

How far should a generator be from a window?

A generator should be at least 20 feet from any window, door or vent, according to the CDC, and the CPSC adds that the exhaust must point away from them. Close the windows near the generator and seal vents in the path of its exhaust.

How far should a propane generator be from the house?

A propane generator should stand at least 20 feet from the house, the same as a gasoline one, because the CPSC and CDC rules cover portable generators and the exhaust carries carbon monoxide. Dual-fuel manuals add their own clearances, so read yours as well.

References

1. Centers for Disease Control and Prevention. Carbon monoxide poisoning from hurricane-associated use of portable generators – Florida, 2004. JAMA. 2005;294(12):1482. doi:10.1001/jama.294.12.1482
2. Emmerich SJ, Wang L, Persily AK. Measured carbon monoxide concentrations from stock and reduced-emission prototype portable generators operated in an attached garage. J Air Waste Manag Assoc. 2017;67(8):889-898. doi:10.1080/10962247.2017.1300202
3. Daley WR, Smith A, Paz-Argandona E, Malilay J, McGeehin M. An outbreak of carbon monoxide poisoning after a major ice storm in Maine. J Emerg Med. 2000;18(1):87-93. doi:10.1016/S0736-4679(99)00184-5
4. Lutterloh EC, Iqbal S, Clower JH, et al. Carbon monoxide poisoning after an ice storm in Kentucky, 2009. Public Health Rep. 2011;126(Suppl 1):108-115. doi:10.1177/00333549111260S114
5. Hampson NB, Zmaeff JL. Carbon monoxide poisoning from portable electric generators. Am J Prev Med. 2005;28(1):123-125.
6. Centers for Disease Control and Prevention. Use of carbon monoxide alarms to prevent poisonings during a power outage – North Carolina, December 2002. JAMA. 2004;291(14):1691. doi:10.1001/jama.291.14.1691

Safety Note: Generator exhaust contains carbon monoxide, which can kill in minutes. Run a fuel generator outdoors only, never in a home, garage, basement, shed or other enclosed or partly enclosed space, even with doors or windows open. The CPSC says to place it at least 20 feet from your home and other buildings, with the exhaust pointed away from doors, windows and vents. Install battery-operated or battery-backup carbon monoxide alarms on every level of the home and outside sleeping areas. Never plug a generator into a wall outlet: connect it to a house only through a transfer switch or interlock installed by a licensed electrician. Refuel only with the engine off and cool, and read the manufacturer’s manual, including for a portable power station.