how to run a generator safely

Generators save lives during power outages. They also take lives every single year. The Consumer Product Safety Commission estimates that portable generators cause about 70 carbon monoxide deaths annually in the U.S. and send thousands more to the emergency room. Add in electrocutions from backfeeding, fires from improper refueling, and burns from hot exhaust, and you have a machine that demands respect every time you turn the key.

I wrote this page because too many generator safety guides are either a paragraph long or written by lawyers. This one is written by a guy who runs generators year-round, has made a few of the mistakes on this list (the non-fatal ones), and wants you to avoid all of them.

Read the whole thing. Bookmark it. Tape the short answer to the wall of your garage if you have to. The rules are simple. The consequences of breaking them are not.

carbon monoxide: the invisible killer

This is the section that matters most. If you only read one part of this page, read this one.

Carbon monoxide is a colorless, odorless, tasteless gas. You cannot see it, smell it, or taste it. By the time you feel the symptoms — headache, dizziness, nausea, confusion — you may already be too impaired to save yourself. People fall asleep and never wake up. Entire families have died in a single night because a generator was running in the wrong place.

A running portable generator produces CO at concentrations that can kill a person in minutes in an enclosed space. Not hours. Minutes. A typical 5,000-watt generator produces roughly as much CO as 450 idling cars. That is not a typo.

what CO poisoning looks like

The early symptoms are easy to dismiss, especially at 3 AM during an ice storm when you're already tired and stressed:

• Headache (often described as a dull, persistent ache)
• Dizziness or lightheadedness
• Nausea or vomiting
• Confusion, difficulty thinking clearly
• Weakness or fatigue
• Blurred vision
• Loss of consciousness

If anyone in your house has these symptoms during a power outage while a generator is running, get everyone outside immediately. Do not stop to turn off the generator. Do not gather belongings. Get out and call 911. You can replace a generator. You cannot replace a person.

CO detectors are not optional

If you own a generator, you must own battery-operated carbon monoxide detectors. Not "should." Must. Install them on every level of your home and outside every sleeping area. Test them monthly. Replace batteries annually. Replace the detectors themselves every 5 to 7 years (they have an expiration date on the back).

A CO detector costs $20 to $40. It is the cheapest life insurance you will ever buy. The ones with digital readouts are better than the ones that just beep, because they show you concentration levels before they reach the alarm threshold — you can catch a problem before it becomes a crisis.

placement: the 20-foot rule

Place your generator at least 20 feet from any door, window, vent, or opening to your home. Point the exhaust away from the house and away from any neighboring structures. This is the minimum distance recommended by the CPSC, the NFPA, and every manufacturer I've ever read the manual for.

More distance is better. If you can put it 30 or 40 feet away, do it. CO is lighter than air and can drift in unexpected directions, especially when wind shifts. It enters homes through cracked windows, dryer vents, soffit vents, and gaps around doors that you didn't even know existed.

Practical placement tips:

• Pick your generator's spot before an emergency. Walk out there right now and identify it. Clear the area.
• Make sure the spot is on a flat, stable surface. Generators vibrate. An unstable surface means a tipped generator, which means spilled fuel on a hot engine.
• Keep it away from anything flammable — dry leaves, brush, gas cans, your deck's wood railing.
• Consider your neighbors' windows too. If your generator is 25 feet from your house but 5 feet from your neighbor's bedroom window, you've just moved the problem.
• Run your extension cords out to the generator. Do not bring the generator closer to the house because you have short cords. Buy longer cords.

running a generator in rain and wet weather

Here's the question everyone asks: can you run a generator in the rain? The answer is yes, but with protection. Generators are electrical devices. Water and electricity are not friends. A wet generator can short-circuit, damage the alternator, electrocute you, or simply stop working when you need it most.

But power outages happen during storms. That is literally when you need the generator. So you need a way to keep rain off the unit while maintaining full airflow and exhaust ventilation.

What works:

• Generator running covers (tents). These are purpose-built canopies that fit over your generator like a tent. They keep rain and snow off the unit while leaving the sides open enough for airflow and exhaust. GenTent and similar products are designed for exactly this. They cost $80 to $150 and they work.
• Open-sided canopy or shelter. A small pop-up canopy works if the sides are completely open. The key word is open. You're keeping rain off the top, not enclosing the generator.
• A permanent lean-to or three-sided shelter. If you've committed to a designated generator spot, a small roofed structure with open sides does the job year-round. Open on at least three sides, or two sides plus the exhaust direction.

What does not work:

• A tarp draped over the generator. This traps heat, restricts airflow, and can melt onto the exhaust. It also funnels rain into pools that drip directly onto the machine. Do not do this.
• A fully enclosed shed or box. Same problem as a garage. CO buildup, heat buildup, fire risk. If it has four walls, it's enclosed. Don't put a running generator in it.
• Your garage, carport, or covered porch. Even partially enclosed spaces are not safe. You already know this from the CO section above, but it bears repeating here because "it's raining and I don't want the generator to get wet" is the exact reasoning that leads people to move it into the garage.

Also: operate your generator on a dry surface when possible. Standing water around the generator is a shock hazard. If the ground is saturated, place the generator on a piece of plywood or a pallet to elevate it a few inches. Dry your hands before touching the generator, the cord connections, or the panel. Wear rubber-soled shoes.

refueling: shut it off first. every time.

Gasoline plus hot metal equals fire. This is not complicated, but people get it wrong because they don't want to lose power for the 10 minutes it takes to cool down and refuel. So they pour gasoline into the tank of a running generator with a 400-degree exhaust pipe six inches away. Sometimes nothing happens. Sometimes they spend six weeks in a burn unit.

The refueling procedure, every single time:

1. Turn the generator off.
2. Wait at least 5 to 10 minutes for it to cool down. The engine, exhaust, and fuel system are all extremely hot immediately after shutdown.
3. Remove the fuel cap carefully. Pressure may have built up in the tank.
4. Refuel using an approved fuel container with a proper spout. Don't use a random jug. Don't pour from a 5-gallon can without a funnel or spout — fuel on the engine is fuel on a fire.
5. Wipe up any spills immediately. Gasoline evaporates fast, but the vapors are heavier than air and pool around the base of the generator — right where the exhaust is.
6. Replace the fuel cap. Restart the generator.

Yes, your refrigerator will warm up slightly during those 10 minutes. It will be fine. Your skin will not be fine if gasoline ignites on it.

Fuel storage basics:

• Store gasoline in approved containers only — the red plastic ones rated for fuel storage.
• Keep fuel containers at least 20 feet from the generator and any other ignition source.
• Treat stored gasoline with fuel stabilizer. Untreated gasoline starts degrading within 30 days. With stabilizer, it lasts up to a year.
• Never store gasoline inside your house or in an attached garage. Fumes accumulate and a single spark — from a water heater, a dryer, a light switch — can ignite them.
• Rotate your fuel. Use the oldest fuel first and replace it with fresh. Mark the date on the container.

backfeed: the thing that kills lineworkers

Backfeeding means connecting a generator to your home's electrical system without a transfer switch, typically by plugging a male-to-male cord (called a "suicide cord" for a reason) into a wall outlet. This sends power backward through your breaker panel and out to the utility lines.

Here's what happens: a lineworker is up on a pole in the rain, working on a line they believe is dead because the grid is down. Your generator is pushing 240 volts through that "dead" line. The lineworker contacts it and is electrocuted. They fall 30 feet. They might die. This happens. It is not theoretical.

Beyond the lethal risk to lineworkers, backfeeding can also damage your generator when grid power is restored — the utility's voltage will surge back through the connection and potentially destroy the alternator. It can also overload your home's wiring because the cord and outlet aren't rated for the loads you're sending through them, which starts fires.

There is no scenario in which backfeeding is acceptable. None. If you cannot afford a transfer switch right now, run extension cords from the generator directly to the appliances you need. That is the safe option. The transfer switch can wait until your next paycheck. The extension cords work tonight.

I wrote a full guide on choosing and installing a transfer switch: transfer switch guide. If you own a portable generator and you want to power more than a couple of appliances, it's worth reading.

extension cord safety

If you're running appliances off a generator without a transfer switch, you're running extension cords. And the cord you use matters more than most people think.

Use the right gauge. Extension cords are rated by wire gauge — the lower the number, the thicker the wire, the more power it can safely carry. For generator use:

• 10-gauge cord: Best for high-draw appliances like refrigerators, freezers, and space heaters. Can handle up to 30 amps depending on length. This is what I use for anything drawing more than 1,500 watts.
• 12-gauge cord: Good general-purpose cord for medium loads — sump pumps, window AC units, multiple lights. Handles up to 20 amps at shorter lengths.
• 14-gauge cord: Acceptable only for very light loads — a lamp, a phone charger. Not appropriate for appliances.
• 16-gauge or thinner: No. These are indoor cords for table lamps. Using one with a generator is how you start a fire.

Cord length matters. The longer the cord, the more voltage drops over distance, and the more heat builds up in the wire. A 10-gauge cord at 25 feet is great. That same cord at 100 feet may not deliver adequate voltage to your appliance, causing the motor to work harder and the cord to overheat. Keep runs as short as practical. If you need distance, go up a wire gauge.

Never daisy-chain extension cords. Plugging one extension cord into another is one of the most common causes of electrical fires during power outages. Each connection adds resistance, generates heat, and creates a potential failure point. If your cord doesn't reach, buy a longer cord. Do not plug two short cords together.

Outdoor-rated only. Indoor extension cords have thinner insulation that breaks down in moisture, heat, and UV exposure. Use cords rated for outdoor use (they'll say so on the jacket, usually marked "W" in the wire type designation).

Inspect before every use. Look for cracked insulation, exposed wire, bent prongs, burn marks, or soft spots in the jacket. A damaged cord is a fire or electrocution waiting to happen. Throw it away and buy a new one.

Keep connections dry. Where the cord plugs into the generator and into your appliances, keep those connections off the ground and out of standing water. You can buy weatherproof cord covers for a few dollars, or improvise with a plastic container with notches cut for the cords. Wet connections trip breakers at best and electrocute you at worst.

don't overload the generator

Every generator has two wattage ratings: running watts (what it can sustain continuously) and starting watts (the temporary surge it can handle when a motor kicks on). You need to stay within both limits.

When a refrigerator compressor starts, it draws 2 to 3 times its running wattage for a few seconds. A 200-watt fridge might spike to 600 watts on startup. If that spike exceeds your generator's starting watts, the generator overloads. It may trip a breaker, stall, or shut down entirely. In the worst case, it damages the generator or the appliance.

How to avoid overloading:

• Add up the running wattage of everything you plan to connect. Stay well below the generator's rated running watts — I aim for 75% or less.
• Account for the highest starting wattage in your load. The biggest motor you'll start (usually the fridge or the AC) sets your minimum starting-watt requirement.
• Plug in appliances one at a time. Don't connect everything and then start the generator. Start the generator first, then add loads gradually.
• If the generator bogs down, the lights dim, or you hear the engine laboring — you've exceeded capacity. Remove the last load immediately.

If you're not sure what your appliances draw, use my generator sizing guide which has wattage tables for common household items. Or check the label on the back of each appliance — it lists the wattage or amperage (multiply amps by 120 to get watts).

Overloading a generator doesn't just shut it down. Sustained overloading causes the engine to overheat, accelerates wear on the alternator, and can produce unstable power that damages sensitive electronics. A generator operated within its rated capacity will run for years. One that's consistently pushed past its limits won't last two seasons.

grounding your generator

Whether you need to ground your portable generator depends on how you're using it. If you're plugging appliances directly into the generator's outlets using extension cords, most modern portable generators are designed as a separately derived system and do not require an additional ground rod. The frame of the generator serves as the grounding path.

However, if your generator is connected to your home's wiring through a transfer switch, it must be grounded according to your local electrical code. In most cases, this means driving a copper ground rod at least 8 feet into the earth and connecting it to the generator's grounding lug with a copper grounding wire (typically 6-gauge or 8-gauge).

When in doubt:

• Check your generator's manual. It will specify whether a separate ground rod is required.
• Check your local code. Some jurisdictions require grounding in all configurations.
• If you have a transfer switch, you almost certainly need a ground rod. The electrician who installed your transfer switch should have handled this. If they didn't, call them back.

Grounding protects against electrical shock in the event of a fault — a damaged wire touching the frame, a short circuit inside the generator, moisture causing a ground fault. Without proper grounding, the generator frame can become energized, and touching it becomes the path to ground. Through you.

children and pets near generators

Generators are loud, hot, and surrounded by exhaust. They're also fascinating to a four-year-old and a golden retriever.

Keep children and pets away from the generator at all times. This is not a suggestion. The exhaust can reach 500 degrees or more. The muffler and engine block stay dangerously hot for 15 to 20 minutes after shutdown. Extension cords running across your yard become trip hazards in the dark. And a child or pet knocking into the generator or pulling on a cord can create a cascade of problems — spilled fuel, disconnected loads, contact with hot surfaces.

Practical measures:

• Establish a "no-go zone" around the generator. I tell my kids the rule is 10 feet minimum, no exceptions, no matter what.
• If possible, position the generator behind a barrier — a fence section, a row of cinder blocks, something that creates a physical boundary. It doesn't have to be elaborate. It just has to exist.
• Run extension cords along fence lines or house walls, not across walking paths. Secure them with cord covers or tape if they must cross a path.
• Never leave a running generator unsupervised around children. If you need to go inside, bring the kids inside first.
• Pets are more unpredictable than kids. A dog can chew through a cord or knock over a fuel can. Keep them leashed or indoors when the generator is running.

general operating rules

Everything above covers the major hazards. Here are the remaining rules that keep you and your equipment safe:

Read the manual. I know. Nobody reads manuals. Read this one. Your generator's manual contains model-specific safety information, maintenance schedules, oil specifications, and operating procedures. It takes 20 minutes. Do it before you need the generator, not during the outage.

Test monthly. Start your generator and run it under load for 15 to 20 minutes at least once a month. This circulates oil, burns off moisture, keeps seals lubricated, and proves the thing actually works. A generator that's been sitting in a shed for two years is not a generator. It's a prayer.

Maintain the oil. Check the oil before every use. Change it according to the manufacturer's schedule — typically every 50 to 100 hours of operation, or at least once per season. Running a generator on low or dirty oil will seize the engine. A $12 oil change prevents a $600 engine replacement.

Use fresh fuel. Gasoline goes stale. Ethanol-blended fuel (which is most fuel these days) is even worse — it absorbs moisture and degrades faster. Use fuel stabilizer in every can you fill. If the generator has been sitting with untreated fuel for more than 60 days, drain the old fuel and start fresh. Old fuel is the number one reason generators won't start when you need them.

Let it cool before covering or storing. After you shut the generator down, give it 30 minutes to cool before you put a cover on it or move it into storage. A cover on a hot generator traps heat and can melt. Moving a hot generator risks burns and increases the chance of a fuel spill from a warm, pressurized tank.

Never operate indoors. Never. I've said it four times on this page. I'll say it once more. Not in your house. Not in your garage. Not in your basement. Not in a shed. Not under a carport with walls. Not in a tent. Not ever.

a checklist to tape to the wall

Cut this out. Tape it where you store the generator. Follow it every time.

1. Generator is placed 20+ feet from any opening, exhaust pointing away
2. CO detectors are installed and working inside the house
3. Generator is on a flat, stable, dry surface
4. Rain cover or canopy in place if wet weather
5. Oil checked and at proper level
6. Fresh, stabilized fuel in the tank
7. Generator started and warmed up before connecting loads
8. Appliances connected one at a time, watching for overload
9. Heavy-duty outdoor extension cords only (10 or 12 gauge)
10. No daisy-chained cords
11. Cord connections off the ground and dry
12. Children and pets kept clear
13. Transfer switch engaged if connected to house wiring (never backfeed)
14. Generator shut off and cooled before refueling
15. Fuel stored in approved containers, 20+ feet from generator

If you're looking for the right generator in the first place, start with my best portable generator picks. If you need help figuring out what size, I wrote that up too. And if the power just went out and you found this page by searching on your phone, go read what to do when the power goes out — it's a step-by-step checklist for right now.

More in the guides section and across the generators section of this site.