Automatic transfer switches

What the transfer switch does

The transfer switch sits between the utility service, the generator and your panel. When it senses that grid power is gone, it signals the generator to start, waits for steady output, then switches your circuits over. When the grid returns, it switches back and lets the generator cool down and stop.

Just as important, it keeps the two power sources apart. Generator power must never flow back onto utility lines, where it can injure line workers who think the line is dead. A properly installed transfer switch prevents that.

Whole-house or essential circuits

A service-rated whole-house switch, often 200 amps for a typical home, transfers the entire panel. An essential-circuit switch moves only selected circuits, such as heat, well pump, fridge and some lights, to a smaller subpanel. Whole-house switches pair well with load management modules that hold back big appliances like central air until the generator has room. Your contractor recommends a setup based on your panel and the generator size.

Automatic versus manual

Standby generators use automatic switches. Portable generators are usually connected through a manual transfer switch or a panel interlock, where someone flips the switch by hand. See our page on portable generator hookups for that option.

Permits and who should do it

Installing a transfer switch is electrical work inside or next to your main panel. It needs a qualified, licensed electrician, and most villages and towns require a permit and inspection. This is not a do-it-yourself job. Ask your contractor to include the permit in the quote.

• Ask what amperage the switch is and whether it is service rated
• Ask whether load management is included or needed
• Ask whether the switch matches the generator brand and controller
• Confirm the contractor's Westchester County license and insurance

Replacing an older switch

If your generator is being replaced, the existing transfer switch may or may not work with the new unit. Some brands require their own switch for the controls to talk to each other. Ask the contractor to confirm compatibility before you assume you can keep the old one.

What to expect on install day

Power to the house is usually shut off for part of the day while the electrician connects the switch to your service and panel. Plan for the fridge, internet and well pump to be off for a few hours, and ask the contractor for a rough window ahead of time. Once everything is connected, the installer should test the switch by simulating an outage so you can see the generator start and take the load, then return the house to utility power.

After the inspection passes, keep the switch area clear and accessible. Do not open the switch cover or try to adjust it yourself. If the switch fails to transfer during an outage, call a technician.

Typical transfer switch costs

Published national ranges for the switch plus installation.

Ranges are national averages from the source below, not quotes. Panel upgrades and long wire runs add cost.

Sources: Angi, transfer switch installation cost