A transfer switch is the safe way to run house circuits from a portable generator. It lets you choose utility power or generator power for a set of selected circuits, so the generator can never feed back into the utility lines. CPSC warns never to power house wiring by plugging a generator into a wall outlet (“backfeeding”). That puts utility workers and neighbors at risk of electrocution and bypasses household circuit protection. Installing a transfer switch is panel work for a licensed electrician. Your part is planning.

How a typical setup works

A CPSC staff description of a typical residential setup says the circuits you want backed up are moved from the main panel into a separate transfer-switch panel. One cable runs from the main panel to that panel, and the generator connects to it through a cord. In normal use, those circuits run on utility power. During an outage, you start the generator outdoors, open the utility breaker in the transfer-switch enclosure, then close the generator breaker.

The same staff paper gives two reasons people choose this over extension cords: fewer long cord runs, and the ability to power hard-wired loads such as a furnace blower, lighting circuits, sump pumps and well pumps.

Plan before you call an electrician

  1. List the essential loads. CPSC staff note that most portable generators can supply only part of a home, so pick the circuits that protect heat, water, food and communication: the furnace blower, sump pump, refrigerator, a few lights and internet equipment.
  2. Check the generator’s outlet and rating. The transfer switch, inlet and cord must match the generator’s outlet and output, and the selected loads must stay within what the generator can run, including motor startup surges.
  3. Choose the generator’s operating spot first. CPSC says to run it outside, at least 20 feet from the house, with the exhaust pointed away from the home and any other building people can enter. Not in a garage, porch, carport, basement, crawlspace or shed, even with the doors open. Put the power inlet where a cord can reach that spot without crossing a doorway.
  4. Ask about permits. Panel work commonly needs a permit and inspection. Ask each electrician to include it in the quote.

What drives the cost

No single price fits every house. Get itemized quotes that separate the transfer equipment, the inlet and cord, the number of circuits moved, the cable route from panel to inlet, any panel upgrades, the permit, and wall repair. A panel on an outside wall near the generator spot is usually simpler than one across the house.

Safe operation during an outage

  • Install battery-operated or battery-backup CO alarms. CPSC says to put them on each level and outside sleeping areas and to test them monthly.
  • If anyone feels sick, dizzy or weak while the generator runs, get to fresh air immediately.
  • Keep the generator dry without moving it indoors or near openings. CPSC suggests an open, canopy-like structure on a dry surface where water can’t pool.
  • Turn the generator off and let it cool before refueling. Store fuel outside living areas in labeled, non-glass safety containers.
  • Use only intact, outdoor-rated cords, with the full length free of cuts and all three prongs on the plug.

Before the first storm

Label the backed-up circuits by load (“sump pump,” not “basement”). Keep the switchover steps next to the panel, and do a test run while the weather is calm. Follow the generator manual’s schedule for exercise runs, oil and fuel.

FAQ

Can a portable generator transfer switch power my whole house?

Usually not. CPSC staff note that portable generators generally have enough capacity for only part of a home’s equipment, so a typical transfer switch serves a few selected circuits.

Why not just plug the generator into a wall outlet?

That’s backfeeding. CPSC warns it is extremely dangerous, creates an electrocution risk for utility workers and neighbors on the same transformer, and bypasses some household circuit protection.

Do I need an electrician to install it?

Yes. The work involves the main panel, moving circuits and routing cable, and it often needs a permit. You can do the planning yourself: the load list, the generator’s outlet rating and the inlet location.

How far from the house should the generator run?

CPSC says to operate portable generators outside, at least 20 feet from the house, with the exhaust pointed away from the home and any other occupied building. Never run one in a garage, porch, carport, basement or shed.

Sources