Guides

How Far From the House Should a Generator Be?

By Outage Sizer · Published October 20, 2026

A portable generator should run outdoors at least 20 feet from any door, window or vent, and never inside a home, garage, shed or crawlspace. That distance is the one figure the federal agencies agree on, and it applies whatever size generator you choose.

What each agency says

• U.S. Consumer Product Safety Commission (Portable Generator Hazards safety alert (pub. 5123)): "Keep them at least 20 feet from doors, windows, and vents that could allow CO to come indoors."
• Centers for Disease Control and Prevention (Use a Generator Safely): "When you're using a generator, keep it outside at least 20 feet away from any doors, windows, or vents."
• Occupational Safety and Health Administration (Using Portable Generators Safely (OSHA 3286)): "Do not use a generator outdoors if its placement near doors, windows, and vents could allow CO to enter and build up in occupied spaces."
• Federal Emergency Management Agency (Be Safe During a Power Outage): "Generators, camp stoves, or charcoal grills should always be used outdoors and at least 20 feet away from windows so you and your family stay safe from carbon monoxide."
• U.S. DOE Building America Solution Center (Generators for Back-up Power During Outages): "Keep the generator at least 20 ft from the home."

The CPSC adds: "NEVER use inside a home or garage, EVEN IF doors and windows are open." FEMA: "Do not use a generator indoors or in partially enclosed spaces- including homes, garages, and crawl spaces even those areas with partial ventilation."

Why 20 feet

A generator engine makes carbon monoxide, a gas you cannot see or smell. Exhaust that reaches an open window, a door or an air intake can build up inside the house. The 20-foot figure is a minimum, not a target; OSHA puts it as a test rather than a distance: "Do not use a generator outdoors if its placement near doors, windows, and vents could allow CO to enter and build up in occupied spaces."

Carbon monoxide alarms

The CPSC also says to "install battery-operated CO alarms or plug-in CO alarms with battery back-up in your home". Battery backup matters because the alarm has to work during the same outage the generator is running for. Test the alarms before the storm season.

Getting the power inside safely

Twenty feet of distance means a heavy-duty outdoor extension cord for each appliance, or a transfer switch that feeds selected circuits. What you must not do is plug the generator into a wall outlet: OSHA warns that connecting a generator to house wiring without a transfer switch creates "a risk of electrocution for utility workers and others in the area.". The transfer switch guide explains the options.

Rain and snow

None of the agencies relaxes the placement rule for bad weather, which is exactly when generators run. Plan for keeping the generator dry where it sits, outdoors and 20 feet out, rather than moving it closer to the house.

Before you need it

• Decide where the generator will sit, 20 feet from openings, and check the spot works for your cords or inlet.
• Fit battery-backed CO alarms on every level.
• Work out what you want to run with the calculator, so the generator is big enough without stringing extra appliances on overloaded cords.

Keep the generator outdoors and at least 20 feet from doors, windows and vents every time it runs.

Sources

• U.S. Consumer Product Safety Commission, Portable Generator Hazards safety alert (pub. 5123)
• Centers for Disease Control and Prevention, Use a Generator Safely
• Occupational Safety and Health Administration, Using Portable Generators Safely (OSHA 3286)
• Federal Emergency Management Agency, Be Safe During a Power Outage
• U.S. DOE Building America Solution Center, Generators for Back-up Power During Outages