How to Safely Run a Portable Generator During a Power Outage

A portable generator solves the immediate problem of a power outage, but it introduces a few of its own — carbon monoxide, backfeeding, and overloaded circuits are the three ways a generator turns a blackout into a bigger emergency. None of the precautions below are complicated, but skipping any one of them is how people get hurt or burn out expensive appliances.

This covers the setup and operating steps that apply to any portable generator, gas or dual-fuel, whether you're running a few extension cords to essential appliances or connecting through a transfer switch to your home's wiring.

Placement: outdoors, away from windows, and never in a garage

Carbon monoxide from a running generator is colorless and odorless, and it builds up fast in any enclosed or partially enclosed space — a garage with the door open, a covered porch, or even a breezeway between the generator and the house. Run a generator outdoors, at least 20 feet from the house, with the exhaust pointed away from windows, doors, and vents, every time, not just when it's convenient.

A battery-powered carbon monoxide detector inside the house is cheap insurance on top of correct placement — it won't prevent a generator from producing CO, but it gives you a warning if exhaust is finding its way in regardless.

Never backfeed through a wall outlet

Plugging a generator into a wall outlet to power your house's wiring backward — backfeeding — can energize circuits throughout the house and the utility lines outside it, which risks shocking you, your neighbors, or a utility worker trying to restore power. It's dangerous and illegal in most areas, no matter how careful the extension cord setup looks.

If you want a generator to power your home's wiring and circuits rather than running a few appliances on extension cords, the only safe way is a transfer switch or interlock kit installed by a licensed electrician. See our best generator transfer switches & interlock kits roundup for how the hardware options compare.

Size the load before you plug anything in

Overloading a generator doesn't just trip a breaker — it can damage the appliances plugged into it and shorten the generator's own life. Add up the running watts of everything you plan to power at once, then add the single largest starting-watt surge (usually a refrigerator or sump pump), and keep the total under the generator's rated output rather than its absolute max.

If you haven't worked through this math for your own household yet, our what size generator do I need guide walks through it step by step, and our best portable generators roundup covers picks by output tier if you're sizing up.

Fuel safety: never refuel a hot or running generator

Gasoline (and the fumes above it) can ignite on a hot engine or muffler, so let a generator cool for a few minutes after shutting it down before refueling — never top off the tank while it's running or still hot to the touch. Keep spare fuel in approved, sealed containers well away from the generator itself while it's running.

Store spare fuel and the generator itself somewhere ventilated, and treat any fuel that's been sitting for more than a month or two with stabilizer before use — our winterizing outdoor power equipment checklist covers fuel storage in more depth if the generator's about to sit unused for a while.

Keep it dry

A portable generator needs to run in a dry spot, ideally under a purpose-built generator canopy or tent rated for ventilation and rain, never directly exposed to rain or standing in a puddle. Water and a live generator are a shock and short-circuit risk, and a wet control panel can mean the generator refuses to run at all right when you need it.

Keep the cord and connection points elevated off wet ground too, and use outdoor-rated, GFCI-protected extension cords for anything running off the generator to the house.

Use the right extension cords

Running appliances straight off the generator with extension cords (rather than through a transfer switch) is the normal setup for partial backup, but an undersized or overly long cord can overheat or drop voltage enough to strain whatever's plugged into it. See our extension cord gauge guide for the correct wire thickness by amp draw and distance before running a long cord from the generator to the house.

Plug high-draw appliances — a refrigerator, a window AC unit, a sump pump — directly into the generator's outlets where possible rather than daisy-chaining cords or power strips, which adds resistance and risk at every connection point.