Home generators and transfer switches: what an electrician needs to do

Updated November 10, 2026 · KeystoneProGuide editorial team

Can you plug a generator into the house?

Not through a wall outlet, and not without a transfer switch. The Pennsylvania Public Utility Commission's storm advice is to run generators outdoors and connect devices directly to the generator, not to your home's wiring, to protect utility workers. The Electrical Safety Foundation, a nonprofit safety group, says the same: do not plug a generator directly into the home, and connect what you need to power straight to the generator.

The reason is backfeed. The foundation explains that a generator connected to the house wiring can become a power source for the surrounding area, and that the backfeed can follow the wires and harm people nearby, including utility workers repairing the lines. It can also damage your home and your neighbor's.

What does a transfer switch do?

It makes the house take power from one source at a time. The foundation says transfer switches, manual or automatic, let you choose between utility power and generator power, and that they are the only way to safely power your home's electrical system from a generator. They isolate the two sources so backfeed cannot happen, and they also protect the home from fires caused by short circuits and improper connections.

The foundation says transfer switches should be installed only by a qualified electrician. This is the electrical part of a generator project, and it is the part to plan before an outage, not during one.

Does this apply to standby generators too?

Yes. The foundation's generator advice is written for both portable and standby generators used for backup power, and its transfer-switch rule does not distinguish between them. The CPSC's carbon monoxide warnings below are aimed at portable units.

Where must a generator be placed?

Outside, well away from the house. The Consumer Product Safety Commission says carbon monoxide from portable generators can kill in minutes, and that on its latest figures an average of nearly 100 people die in the U.S. each year from CO poisoning caused by portable generators. Its rules:

• Never run a portable generator inside a home, garage, basement, crawlspace, shed or other enclosed space. Opening doors or windows does not provide enough ventilation.
• Run it outside only, at least 20 feet from the house, and not on a porch or in a carport.
• Point the exhaust away from doors and windows, and close windows near the generator.
• Install CO alarms on every level and outside sleeping areas, and test them monthly.

The foundation adds 3 to 4 feet of clear space above and on all sides, grounded and undamaged cords of the right rating, ground-fault protection, keeping the generator dry, and refueling only when it is cool.

Which portable generators are safer?

The CPSC recommends looking for portable generators with a carbon monoxide shut-off feature, which turns the engine off when CO builds up nearby. It says models certified to the PGMA G300-2023 and UL 2201-2023 standards include CO safety technologies, and that UL 2201 certified models also have reduced CO emissions.

Does a generator hookup need a permit?

Usually. Installing a transfer switch adds wiring to the home's electrical system, and Pennsylvania's code regulation requires a permit before an electrical system is installed or altered, with an exemption only for ordinary repairs. Some townships have a form just for it: Nockamixon Township in Bucks County and Haverford Township in Delaware County both list a generator permit application among their permits.

In Philadelphia, the city's electrical permit page says emergency generators may require a permit from the Department of Public Health, for installing new equipment or operating it, as well as the electrical permit that a licensed electrical contractor must pull.

What does it cost?

The published figures vary widely.

These are national figures from home-services cost sites, given as they publish them. Neither publisher explains the width of its range in a way that would let you place your own job in it, so ask each electrician to price the same scope: the same generator size, the same switch and the same circuits.

What should you ask before buying?

• Which circuits do you need during an outage, and can the generator carry them?
• Will you install a manual or automatic transfer switch, and does the price include the permit?
• Where will the generator sit, and does that location meet the CPSC's 20-foot guidance?
• For a portable unit, does it have a CO shut-off feature?
• For a standby unit in Philadelphia, is a Department of Public Health permit needed?

Which parts of a generator setup a homeowner can handle, and which belong to an electrician, are covered in doing it yourself or hiring. Prices for other jobs are in the cost guide, the checks on a contractor are in how to choose an electrician, and electricians are on the electricians directory page.

Sources

1. Winter Storm May Knock Out Power; CPSC Warns of Deadly Carbon Monoxide and Fire Risks, U.S. Consumer Product Safety Commission
2. CPSC Warns of Generator, Carbon Monoxide and Fire Hazards Ahead of Hurricane Season, U.S. Consumer Product Safety Commission
3. Generator Safety, Electrical Safety Foundation International (ESFI)
4. Don't Shock the Neighborhood, Electrical Safety Foundation International (ESFI)
5. Prepare Now for Post-Christmas Winter Storms - PUC Shares #UtilitySafety Tips, Pennsylvania Public Utility Commission
6. How Much Does an Electrician Cost to Hire? [2026 Data], Angi
7. How Much Does an Electrician Cost in 2026?, HomeAdvisor
8. How Much Does it Cost to Hire an Electrician?, Fixr
9. Get an Electrical Permit, City of Philadelphia
10. Permits & Forms, Nockamixon Township
11. Building & Codes Department, Township of Haverford
12. 34 Pa. Code § 403.62. Permit requirements and exemptions., Commonwealth of Pennsylvania (Pennsylvania Code)