A portable generator can be your best friend when the power goes out. But there are limits to the convenience you’ll enjoy until you connect that generator to your home’s electrical panel. Until you do, household systems such as your air conditioner won’t run; you’ll also have to run extension cords throughout your home in order to connect individual devices.
In short, you’re really going to want to connect that portable generator.
When you do, you’re going to need a transfer switch, or an interlock kit that performs a similar role. Don’t even think of not using one. Connecting your generator directly to an appliance or an electrical outlet would be a violation of electrical code and, more importantly, extremely dangerous.
Transfer switches create a connection from one power source, such as your neighborhood’s power line, while breaking the connection to the other (your generator); throw the switch, and the connection changes to the other source. This ensures that you can’t draw power from more than one source, or feed power into more than one destination.
Without a transfer switch to isolate the power, power can travel in the wrong direction – such as out of your home into the neighborhood’s utility lines. This is called backfeed. If power travels from your home to a nearby transformer, the transformer could attempt to power high-voltage utility lines. A neighborhood line that shouldn’t have power could suddenly be carrying thousands of volts – a potentially deadly jolt to a utility worker.
Now that you understand why you need a transfer switch, let’s look at the two basic types: a manual transfer switch (or an interlock kit), and an automatic transfer switch.
Manual transfer switches require you, the operator, to manually select one power source or another. For example, if your neighborhood loses power, you would personally break the connection to your neighborhood line in favor of the one to your generator; the same is true of interlock kits. Neither manual transfer switches not interlock kits will select the power source on their own.
Automatic transfer switches have the added benefit of being able to sense if power is coming in through the utility line. When utility power goes out, the automatic transfer switch will break the connection to the power line; within seconds, a backup generator will engage and power the home until utility power is restored. Both automatic transfer switches (and the accompanying backup generators) are larger, more sophisticated, and more expensive solutions.
It is worth mentioning that, while manual transfer switches and interlock kits can allow you to provide power to your home’s electrical system, most portable generators cannot power an entire home. Instead, both of these options allow you to connect only to select circuits in your home. For example, you may be able to power your refrigerator and other larger devices, but you’ll need a larger generator to power your heating and air system.
For most of us, however, installing a manual transfer switch or interlock kit provides a sensible, reasonably priced upgrade to the convenience a portable generator can provide on its own.