Updated: December 19, 2020

How to Connect a Portable Generator to a House

by Charles Jasper

When the power goes out, a portable generator is an excellent way to ensure that your family stays safe from extreme temperatures, to keep your food from spoiling, and to remain connected to important information and news.

Power outages are most common during times of extreme weather. The extreme heat is dangerous for the old and the young and uncomfortable for everyone. The cold that comes with snow and ice storms that knock out power is life-threatening for anyone left without heat. When it’s down trees from high winds and thunderstorms that cause an outage, you need to be able to get news updates without interruption.

How to Connect a Portable Generator to a House

Ways to Connect

While you could crack a window and run extension cords throughout your house, it’s safer and more convenient to connect your generator directly to your home’s electrical system. Ultimately, this connection can be made by anyone, but it is important to ensure that it is done correctly to avoid hazards that include fire and electrocution. If you have concerns, consider hiring an insured electrician to complete the work.

There are a few different ways to safely and legally connect your generator directly to your house power:

● Automatic Transfer Switch – You need to know that this option requires that your generator be dedicated to backing up your house power. It is convenient, but you won’t be able to use your generator for anything else.
● Manual Transfer Switch using a sub panel – These are great for use with portable generators. They won’t connect to your whole home, though. You’ll want to choose a few of your most important breakers to connect to using this switch.
● Breaker Interlock – This switch requires that you manually switch over to breaker power, but it’s easy to do. You can make the switch in under five minutes, in most cases.

Step 1

How to Connect a Portable Generator to a House

Consider your power need. Do you want to be able to run all your appliances including your furnace, freezer, TV, washer, and dryer? Maybe you just need enough power to keep some essentials going like your fridge and freezer along with some lights or a fan. You will need to choose a connection method that aligns with your power needs.

The easiest way to ensure that your connection and generator will live up to your expectations is to list out the appliances you want to run along with their energy requirements. From there you can begin looking at options that will meet those needs. You may even want to consider setting up two generators to run in parallel, but again, be sure to connect them safely.

Step 2

Take the time to do a little research about the codes and safety requirements specific to your locality. In some places, an interlock is illegal, so you might need to choose a different method of connection. Other locations may require that the work be completed by a certified electrician. Whatever your local regulations require, remember that you are ultimately responsible for any code violations.

Step 3

Do a safety check. This step should be completed while you are researching for step two, however, it is important enough to discuss separately. There are many creative ways that people have connected their generators to their homes. One of the most common is to simply use a cord with two male ends to plug the generator directly into the house’s electrical system. There are concerns with any plan that isn’t approved and up to code.

Illegal

It is illegal in almost every location in the United States to use a male/male cord to connect a generator directly into a house and for good reason.

Fire Hazard

Your generator will likely create more energy than the cord can handle. Since your house will try to use as much power as is available, the power flowing through the line can overwhelm the cord and start a fire.

Risk of Injury & Death

When an electrical system is up to code, power is easy to shut off in the event that someone is being electrocuted. When you bypass your breaker and directly connect power, you remove that safety feature and risk turning injuries into deaths.

Lawsuit

Power can feedback to the electric grid when you plug directly into your house. This is the reason direct connection methods are outlawed, so the power company can sue you for any injuries to their workers that happen as a result of your connection.

Step 4

How to Connect a Portable Generator to a House

Check the amperage listed next to the big, round plug on your generator. It will likely list either 30-amp, 40-amp, or 50-amp. There are some exceptions, but those are the most common. It is very important that you know this number.

When you purchase your other supplies, you will want to ensure that everything matches that amperage. So, if you have a 40-amp outlet on your generator, you should use a 40-amp extension cord for your generator along with a 40-amp power inlet box and connections.

Step 5

Decide the best connection method to meet your needs and ensure that your home remains up to code. By now, you should have a list of the appliance you want to run, and the amount of energy required to make it happen. Choose your connection method and gather your materials. You should also read all the directions very carefully.

If you have any questions or concerns about the directions that go with any of your supplies, consider bringing in a professional electrician. It is never worth risking the safety and health of your family unless you are completely confident in what you are doing.

Step 6

You will need to drill a hole to get let a cord run power from your outdoor generator to your indoor electricity. Many people already have holes run through their foundation for various other reasons. If you can avoid drill a new hole, do so but know that you will want the hole to be as close to the panel box as possible.

If there aren’t any, you will need to drill. A hammer drill is the best tool for this job. Be sure to measure several times before drilling. You don’t want to accidentally drill into the panel!

Step 7

If you have chosen an interlock, you will need to mount the box outside your home. Place it carefully to ensure that it is near both your generator and your indoor panel. It should also be near the hole you have drilled.

Step 8

Make sure that you have space in your indoor breaker box. Most interlock systems require that a specific part of your panel box be available. If you are not comfortable working with the breaker box, or if it is illegal for a homeowner without an electrical license to do this work in your area, be sure to hire a professional.

How to Connect a Portable Generator to a House

Step 9

Wire the inlet portion of the electric, so that the power from your generator can pass to the interlock box on the outside of your house. Be sure to use a wiring diagram to plan out the schematics of your wiring and ensure that you know which wires are serving each purpose.

Step 10

It’s time to move indoors. Run your wires through the wall. Almost all localities require that you use some form of a junction box to mark this spot. Be sure that you are familiar with those requirements and that you have followed all local codes and regulations.

Step 11

Now that your wires are inside, begin connecting them to your breaker box. Again, you should be referring to your wiring diagram to ensure that everything gets properly connected. Use a wire splice as needed to ensure that all connections are up to code.

Step 12

Make sure that you have your ground wire connected to the correct place. Check that all of your colored wires are connected to the correct place and that all of your connections are secure. You will soon be testing your system, so this is your chance to double-check all of your work.

Step 13

It’s the moment of truth. Get your generator up and running and switch the power to your generator before turning off the main power to your house.

Step 14

Test out the appliances that you have connected to the generator and watch for any concerning signs. If there appear to be any issues, immediately turn off power to the generator and shut it down. If you aren’t sure exactly what is wrong, call a professional electrician.

Summary

One of the biggest conveniences of owning a generator is the ability to keep your house running, even when the power goes out. Using the proper method of connection and installing it correctly can result in an easy conversion from the power grid to your generator’s power.

The most important consideration when connecting your generator to your home is safety. This may be a job for which you want to hire a professional, insured electrician. If you choose to make the connection yourself, be sure to follow all local codes and regulations.

About the author

Charles Jasper is the owner and main author of Generator Guider. He has a degree Engineering and 20 years experience on using generators on various projects, around the house, and while traveling and camping. He has a passion for everything related to home improvemen and loves to travel on his RV. When he is not working, you might find Jasper working on projects around the house or organizing a camping trip.