How to Run a Generator Safely (+ Power Outage Checklist)

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The storm has passed, the street is dark and the first generators are starting up down the block. It’s tempting to set yours just inside the garage door, out of the drizzle. That one choice causes more generator deaths than any other. Running a generator safely comes down to a few simple habits, and you can learn them all before the next outage.

To run a generator safely during a power outage: use it only outdoors, at least 20 feet from the house with the exhaust pointed away from doors and windows, never in a garage. Keep battery-powered carbon monoxide alarms on every level. Connect appliances with heavy-duty outdoor cords or a transfer switch, never a wall outlet. Shut it off and let it cool before refueling.

Below: the step-by-step version with the sources behind each rule, maintenance and storage, the safety gear worth owning, and a printable-style power outage checklist.

Why carbon monoxide is the big danger

Generator exhaust contains carbon monoxide (CO), a gas you can’t see or smell. The U.S. Consumer Product Safety Commission (CPSC) says an average of nearly 100 people die in the U.S. each year from CO poisoning caused by portable generators, and that one generator can produce as much CO as hundreds of cars. CPSC warns that CO can build up to deadly levels in a garage, basement or shed even if you try to ventilate it, and can linger for hours after the generator shuts off.

The CDC lists the most common symptoms of CO poisoning as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. If a CO alarm sounds or anyone feels sick, get everyone into fresh air right away and call 911.

How to run a generator safely, step by step

1. Get ready before the storm

• Read the owner’s manual and start the generator once a month or so, so you know it works (Generac recommends running a stored portable for 30 minutes every 30 days).
• Install CO alarms. CPSC says to put battery-operated (or battery-backup) CO alarms on each level of the home and outside sleeping areas, and to test them monthly. The CDC says to place them near every sleeping area.
• Choose the spot now. Find a flat, open place at least 20 feet from the house, away from your windows, doors and vents and your neighbor’s too.
• Have the right cords, or a transfer switch. More on both in step 4.

If you’re buying, NFPA and CPSC both suggest a generator with a CO shut-off that turns the engine off when CO builds up around it. Makers name it differently: Honda CO-MINDER, Champion CO Shield, Generac COsense, Westinghouse “CO Sensor” and DuroMax “CO Alert”; Yamaha calls it a CO sensor with automatic shutoff. NFPA also suggests choosing a generator listed by a nationally recognized testing laboratory. A CO shut-off is a backup, not a reason to run a generator closer to the house. Compare models in our best generators for a house power outage.

2. Place it outdoors, 20 feet or more from the house

• Outdoors only. Never inside the home, garage, basement, crawl space, shed or any partly enclosed space, even with doors or windows open (CPSC, CDC, FEMA). NFPA adds: not in an attached garage, even with the garage door open.
• At least 20 feet away. CPSC says at least 20 feet from the house; the CDC says more than 20 feet from any windows, doors and vents; Ready.gov says at least 20 feet from windows, doors and attached garages.
• Point the exhaust away from your home and other buildings, and close windows and vents near the generator (CPSC).
• Don’t stand downwind. NFPA says if you can smell the exhaust, you’re breathing it.

3. Keep it dry

Water and electricity don’t mix. Generac’s FAQ says never to run a generator directly in rain, snow or other wet conditions. OSHA says to keep it dry and, if needed, protect it with a canopy, and to use GFCI protection around wet or damp areas. CPSC says to follow the maker’s instructions for weather. Any cover must stay open on the sides: moving the generator into a shed, carport corner or garage to keep it dry brings back the CO danger. Touch the generator and cords only with dry hands.

4. Connect appliances the safe way

• Cords: FEMA says to connect appliances with heavy-duty extension cords. OSHA says to use grounded, three-prong cords, inspect them, and never use frayed or damaged ones. Pick outdoor-rated cords whose label rating covers the appliance’s watts, and run them where no one trips over them or closes a door on them.
• House circuits: only through a transfer switch or listed interlock kit, installed by a licensed electrician with a permit where required. See our generator transfer switch guide.
• Never backfeed. FEMA says never to plug a generator into a wall outlet or the main panel: the power can surge onto the lines and injure or electrocute a utility lineworker.
• Don’t overload it. Start the generator first, then add appliances one at a time so their starting surges don’t all hit at once, and keep the total under its running watts. Our generator sizing guide shows the math.

5. Refuel only when it’s off and cool

FEMA puts it plainly: turn the generator off and let it cool before refueling, because gasoline spilled on hot engine parts can ignite. Fuel it outside. Store fuel in properly labeled, non-glass safety containers, away from living areas and from fuel-burning appliances such as a water heater (FEMA). Propane cylinders belong outdoors, standing upright, never indoors, in a crawl space or under the house (North Carolina’s LP-gas standards, which follow NFPA 58).

Use fresh unleaded gasoline; Generac’s FAQ calls for at least 87 octane. Don’t use E15: the EPA’s E15 approval covers newer cars and light trucks, not small engines such as generators and lawn mowers. To see which fuel fits your outage plan, compare gasoline, propane and natural gas, or a dual-fuel generator that runs on two.

6. Look after it: maintenance

NFPA notes that poorly tuned engines make more carbon monoxide, so maintenance is a safety step too. Follow your own manual; Champion’s manuals are typical: change the oil after the first 5 hours of break-in, check the oil before each use (or every 8 hours), and clean the air filter and change the oil every 50 hours or yearly when running under heavy load or in heat. Check cords and plugs for damage before every outage.

7. Store it right between outages

Gasoline goes stale. Generac says fuel kept more than 30 days without stabilizer can deteriorate and damage the fuel system, and recommends draining the tank and running the carburetor dry if you’ll store the generator longer than that. If you keep fuel in it, add stabilizer, run the engine about 30 minutes to circulate it, then shut the fuel valve and let the engine run until it stops; Generac says fuel prepared this way can be stored up to 24 months. Let the generator cool before covering it, and keep it somewhere cool and dry. Rotate stored gas cans: use the oldest in the car and refill with fresh fuel and stabilizer.

Safety gear worth owning

Prices change often. Where we name a price, it’s what we saw at the maker in October 2026; check the current price before you buy.

CO alarms. The Kidde COPD plugs into a wall and keeps working on AA batteries when the power is out, with a digital display you can light up with a button. Battery-only combo alarms are the simplest for bedrooms and hallways during an outage: Kidde’s 30CUD10-V and First Alert’s SMCO210 both run on sealed 10-year batteries and detect smoke and CO. Kidde says CO alarms should be replaced every 7 to 10 years; follow the date on yours.

Check the Kidde plug-in CO alarm price on Amazon

Check the Kidde 10-year smoke + CO alarm price on Amazon

Check the First Alert SMCO210 price on Amazon

Fuel stabilizer. STA-BIL’s maker says its Storage formula keeps gasoline fresh up to 24 months at 1 ounce per 2.5 gallons. Sea Foam says its Motor Treatment stabilizes gas and diesel up to 2 years at a storage dose of 1 ounce per gallon, so a bottle treats fewer gallons. Add it when you fill the can, not months later.

Check the STA-BIL price on Amazon

Check the Sea Foam price on Amazon

Power outage checklist

Print this or save it on your phone. Food rules come from FoodSafety.gov, the USDA and the CDC; the rest from Ready.gov, CPSC and FEMA.

Before an outage

• ☐ A flashlight for every person, plus spare batteries (Ready.gov).
• ☐ Enough nonperishable food and water for everyone (Ready.gov).
• ☐ A power plan for medical devices, made with your medical provider (Ready.gov).
• ☐ CO alarms on every level, tested this month (CPSC).
• ☐ Appliance thermometers in the fridge (40°F or below) and freezer (0°F or below) (CDC, USDA).
• ☐ Frozen containers of water or gel packs, and a cooler ready (CDC, FoodSafety.gov).
• ☐ Generator test-run, fresh stabilized fuel, cords checked, generator spot chosen 20+ feet from the house.
• ☐ Phones and any portable power station fully charged.

During an outage

• ☐ Keep the fridge and freezer closed. Food stays safe about 4 hours in a closed fridge, 48 hours in a full freezer and 24 hours in a half-full one (CDC, USDA).
• ☐ For a long outage, block ice or dry ice keeps the fridge colder (FoodSafety.gov).
• ☐ Unplug appliances and electronics to protect them from surges when power returns (Ready.gov).
• ☐ Generator outside, 20+ feet away, exhaust pointed away; refuel only when off and cool.
• ☐ Use flashlights or battery candles, not open flames; never burn charcoal or run a grill indoors or in a garage (CPSC).
• ☐ Keep portable heaters at least 3 feet from anything that can burn, never unattended, plugged straight into the wall (CPSC).
• ☐ Smell gas? Leave the house and call from outside (CPSC).

After the power comes back

• ☐ Check the thermometers. Throw out perishable food (meat, poultry, fish, eggs, leftovers) that’s been above 40°F for more than 2 hours (USDA, Ready.gov).
• ☐ Frozen food that still has ice crystals or is at 40°F or below can be refrozen or cooked (CDC).
• ☐ Never taste food to decide if it’s safe. When in doubt, throw it out (CDC).
• ☐ If the power was out more than a day, Ready.gov says to discard refrigerated medicine; ask your pharmacist before replacing anything critical.
• ☐ Switch the transfer switch back to utility, unplug cords, shut the generator off and let it cool.
• ☐ Refill and stabilize fuel cans, restock batteries and water, and note what you wished you’d had.

Keep exploring

Start with our home generators guide, then choose between inverter and conventional generators and wire it in with the transfer switch guide. No fumes at all? A portable power station for home backup runs safely indoors, and home battery backup covers whole-home systems. Every generator article is in Generators.

Generator safety questions

How far from the house should a generator be?

At least 20 feet. CPSC says at least 20 feet from the house with the exhaust pointed away; the CDC says more than 20 feet from windows, doors and vents. Farther is better, and keep it away from your neighbors’ windows too. A CO shut-off doesn’t change the distance.

Can I run a generator in the garage with the door open?

No. CPSC, the CDC and NFPA all say never, even with the door or windows open. CPSC says generator CO can kill in minutes, and it can linger for hours after the generator shuts off.

Can I run a generator in the rain?

Not exposed to it. Generac says never to run one directly in rain or snow, and OSHA suggests a canopy. Use a cover that stays open on all sides and keeps the generator outdoors, follow your maker’s weather instructions, and never move it into a garage or shed to keep it dry.

Can I plug my generator into a wall outlet?

No. FEMA says never to plug a generator into a wall outlet or the main panel. The power can flow back onto the utility lines and electrocute lineworkers. Use extension cords to individual appliances, or have a licensed electrician install a transfer switch or listed interlock kit, with a permit where required.

How long can a generator run continuously?

As long as you refuel it safely and keep up with oil checks. For the gasoline generators we track, makers list about 7 to 18 hours per tank at a quarter load. You must shut it off and let it cool before each refill, and Champion’s manuals say to check the oil every 8 hours of running.