Standby or Portable Generator? What Decides It

The difference is how they connect and where they live.

A portable generator is carried out when needed and runs appliances plugged into it, or the house through a transfer switch installed by an electrician. A standby generator is permanently installed outside and wired to the home through a transfer switch. Both burn fuel, and both produce carbon monoxide.

CPSC’s warning is absolute.

The Consumer Product Safety Commission says one generator produces as much carbon monoxide as hundreds of cars, and that it can incapacitate and kill within minutes. Never use a portable generator indoors or in a garage, basement, or shed — even with doors open. Run it outside, well away from windows, doors, vents, and any other opening, and keep a working carbon monoxide alarm in the house.

Backfeeding endangers people you will never meet.

OSHA’s guidance is explicit: never attach a generator directly to a structure’s electrical system unless a qualified electrician has installed a transfer switch. Without one, the generator can energize the utility’s lines for great distances and electrocute utility workers and others. Plugging a generator into a wall outlet with a double-ended cord is exactly this hazard.

Without a transfer switch, plug appliances directly into the generator using the manufacturer’s cords or grounded, three-pronged extension cords rated for the load.

Add up what must run, then check the motors.

List what you actually need during an outage — refrigerator, furnace fan, well pump, a few lights and chargers — and add their running watts. Motors briefly draw more when they start, so the generator must also cover the largest starting load. The generator sizing calculator separates the two.

A standby unit sized for the whole house removes the choosing, at a higher installed cost. A portable unit with a transfer switch for selected circuits covers essentials for less, but depends on someone setting it up safely outdoors during the outage.

Match the choice to how often, how long, and who will operate it.

• Frequent or long outages, medical equipment, or no one able to run a portable unit safely: a standby generator installed by licensed professionals.
• Occasional short outages and a few essentials: a portable generator plus an electrician-installed transfer switch or inlet.
• Either way: carbon monoxide alarms on every level, and a plan for where the generator will sit that keeps it far from the house.

Transfer switches and standby units are electrical, and often fuel-line, work for licensed professionals; ask about permits where you live.