Sales of portable generators tend to spike around major storms, from just before to weeks afterward. But getting a generator up and running in a hurry often means bypassing the recommended installation procedure and making do with extension cords, which can be unsafe. That’s why you should plan ahead and do it right by installing a transfer switch. There's also another way to connect a generator to your electric service that costs significantly less.

Why a Transfer Switch

The power receptacles on a generator are helpful for when you need to power something too far away from your home to use house power. But for the house, a transfer switch lets you easily and safely power what you need most—your refrigerator, furnace or boiler, a sump pump, and more.

Power to your fridge can come from your generator or your utility—not both. The transfer switch works by having a dedicated set of switches for each of the circuits you want to power. Skipping the transfer switch and connecting your generator directly to your electrical service panel could fry appliances, endanger utility workers who might be working on power lines, or damage your generator. You also won't know when utility service is restored unless you see your neighbors' lights go back on.

With a transfer switch (about $500 to $900 to install, including labor), you’ll have one connection to make—plugging one end of a cable into the generator and the other into a dedicated box connected to the transfer switch. You’ll need at least a 5,000-watt generator to use one. Stationary (standby) generators have a transfer switch that automatically comes on when the power goes off.

A Cheaper Alternative

Most manufacturers of service panels and many third-party manufacturers make a small connector called an interlock device. Each is intended for a specific model of panel, but all work the same way: They let you attach your generator to your service panel without a transfer switch but without the hazards of a direct connection.

An interlock kit, $50 to $150, should also be installed by an electrician, who will tell you whether it will work with your electrical system and whether it meets code. When in place, the interlock covers your service panel’s main cutoff switch so that you can’t switch it on while the generator is running. Once utility power is back, you slide the interlock back to its usual position. Power thus flows in only one direction.

Since this route is more manual than using a transfer switch, you’ll need to follow a certain sequence to avoid getting a spike of energy from the generator. But that’s the price you pay to save hundreds on buying and installing a transfer switch.

Looking for a portable or stationary generator? Check our generator buying guide before plugging into our generator Ratings of nearly four dozen portable and stationary models.