The biggest danger with portable generators isn’t the electricity itself. It’s the carbon monoxide they produce. CO poisoning from generators kills dozens of people in the U.S. every year, often during storms when windows are closed and generators are placed too close to the home. Safe generator use comes down to proper placement, correct electrical connections, smart refueling habits, and not overloading the machine.
Placement and Carbon Monoxide
Generator exhaust contains carbon monoxide, a colorless, odorless gas that can kill within minutes in enclosed or semi-enclosed spaces. Early symptoms mimic the flu: headache, dizziness, weakness, nausea, and confusion. People who are asleep or intoxicated can die before they ever notice symptoms.
NFPA 37 requires generators to be placed at least 5 feet from operable windows, doors, and combustible walls. In practice, the farther the better. The Consumer Product Safety Commission recommends 20 feet from any opening. Point the exhaust away from the house, and never run a generator in a garage, even with the door open. Carbon monoxide accumulates faster than ventilation can clear it.
Install battery-operated CO detectors on every level of your home and near sleeping areas. These are your last line of defense if exhaust drifts inside through a window or crack you didn’t account for.
Keeping It Dry in Bad Weather
Most people fire up a generator during a storm, which creates an obvious problem: generators cannot be operated in rain, snow, or standing water. Moisture and electricity are a lethal combination, and water can also damage the engine and alternator.
The solution is a canopy-style generator cover or a purpose-built generator tent that shields the unit from rain while leaving all sides open for ventilation. Never drape a tarp directly over a running generator. It traps heat and exhaust. If you live in a storm-prone area, buying a vented steel or plastic enclosure rated for outdoor use is worth the investment.
Connecting Power Safely
How you connect a generator to your home matters more than most people realize. Plugging a generator directly into a wall outlet or wiring it into your electrical panel without a disconnect device creates something called backfeed. Electricity from your generator flows backward through your panel, out through the utility meter, and into the power lines serving your neighborhood. Line workers restoring power after a storm can be electrocuted by energy they don’t know is there. Your neighbors, assuming the lines are dead, face the same risk.
You have two safe options for powering your home’s circuits:
- Transfer switch: A dedicated, code-compliant device installed next to your electrical panel. It physically disconnects your home from the utility grid before connecting the generator. Transfer switches have clearly labeled controls showing which power source is active, and they make backfeed impossible. This is the safest and most reliable option.
- Interlock kit: A less expensive mechanical device that attaches to your panel and prevents the main breaker and the generator breaker from being on simultaneously. Interlock kits work well when installed correctly, but they rely on manual switching, which leaves more room for mistakes. Not all panels are compatible with interlock kits, and they may not meet local electrical codes.
Either option should be installed by a licensed electrician. If you skip both and simply run extension cords from the generator to individual appliances, you avoid the backfeed problem entirely, though you lose the convenience of powering hardwired systems like your furnace or well pump.
Choosing the Right Extension Cords
If you’re running cords directly from the generator to appliances, wire gauge matters. A cord that’s too thin for the current it carries will overheat, melt its insulation, and potentially start a fire. The longer the cord, the thicker the wire needs to be.
For a 50-foot cord, 12-gauge wire handles up to 20 amps safely, while 14-gauge is fine for 15 amps or less. At 100 feet, you need 10-gauge wire for 20-amp loads and 12-gauge for 12 to 15 amps. A good rule: when voltage drop approaches 5%, step up to the next thicker gauge or use a shorter cord.
Always use outdoor-rated cords in good condition. Inspect them for cuts, frayed insulation, or exposed wire before each use. Never run cords under rugs or through closed doors or windows where they can be pinched and damaged.
Don’t Overload the Generator
Every appliance has two wattage numbers that matter: the steady power it needs to keep running, and the surge it draws during startup. For motor-driven equipment like refrigerators, sump pumps, and air compressors, the starting wattage can be two to three times higher than the running wattage. A circular saw, for example, runs at 1,200 watts but needs 2,400 watts to start. An electric pressure washer runs at 1,200 watts but surges to 3,600.
To size your load correctly, add up the running wattage of everything you plan to power simultaneously, then add the highest single starting wattage from that group. That total is the minimum your generator needs to handle. If you’re running a refrigerator (700 watts running), a few lights (200 watts), and a sump pump (1,200 watts running, 2,400 watts starting), you need a generator rated for at least 3,300 watts surge capacity. Choosing based on running wattage alone will trip the breaker or damage the generator the moment a motor kicks on.
Stagger your startup sequence. Turn on the highest-draw appliance first, let it settle into its running wattage, then add the next one. This avoids stacking multiple surge loads at once.
Refueling Without Starting a Fire
Gasoline vapors ignite easily on contact with hot metal. The engine, exhaust, and alternator on a generator that’s been running are all hot enough to flash-ignite fuel. Always shut the generator off and let it cool before removing the fuel cap. There’s no shortcut here. A few minutes of patience prevents a burn injury or worse.
Keep fuel in an approved HDPE plastic container with a tight-sealing, childproof spout and a built-in vent. Don’t improvise with water jugs or other household containers. Store fuel away from the generator and any ignition source, ideally in a detached shed or garage.
Fuel Storage and Maintenance
Gasoline degrades over time. Untreated fuel left in a generator for months will gum up the carburetor and prevent the engine from starting, which is exactly the scenario you’ll face if you only use the generator during emergencies. Adding a fuel stabilizer at the time of purchase keeps gasoline viable for up to two years in a sealed, properly stored container.
If you’re putting the generator away after a storm, you have two choices: run the engine until the tank and carburetor are completely dry, or fill the tank and add stabilizer, then run the engine for a few minutes so treated fuel circulates through the system. Either approach prevents the varnish buildup that clogs fuel lines and jets.
Check the oil level before every use. Most portable generators will shut off automatically when oil drops too low, but running it to that point still causes wear. Change the oil after the first 20 to 30 hours of use on a new generator, then at the intervals listed in your owner’s manual. Inspect the air filter and spark plug at least once a season, and replace them if they’re dirty or worn.
Grounding Your Generator
Most portable generators used with extension cords don’t require a separate grounding rod, because the frame of the generator serves as the ground. But if you connect the generator to a building’s wiring through a transfer switch, local codes typically require a grounding rod driven into the earth and connected to the generator’s grounding lug with copper wire. Your electrician will handle this during transfer switch installation, but it’s worth verifying.
If you’re using the generator on a construction site or in any setup where the generator frame isn’t the sole grounding point, a dedicated ground rod is required by the National Electrical Code. Check the requirements for your specific use case before assuming the frame ground is sufficient.