Powering a House with a Portable Generator: A Complete Guide

In the case of a power outage, a portable generator can be a lifesaver. However, while more people embrace portable backup generators, others still wonder if they can power a house.

A portable generator can run most, if not all, appliances in your house. It depends on its wattage and your power needs. You can connect the generator using a transfer switch or interlock device to power your home circuit.

Don’t agonize over how you’re going to do it. This article will guide you step by step on how you can run a house using a portable generator. You’ll also get safety tips for the whole operation to protect yourself and everyone else who could otherwise be hurt by mishandling.

Portable Generator Using a Transfer Switch

A transfer switch changes the source of electricity from the primary grid to the backup generator. It could be automatic like those used in businesses with standby generators or manual, where you power it after connecting your portable generator.

You need a manual transfer switch because:

  • It helps to isolate the circuits you don’t need to power and connects to the circuits you need electricity. This prevents overloading and waste of backup power.
  • It separates the house and generator from the main grid to prevent electricity back feeding to the main grid. This prevents fires and hurts the electricity personnel that may be repairing somewhere in the grid system.
  • If the primary grid starts supplying your house with electricity, no fires can erupt because of the double-power sources.
  • It enables the connection of generator power to your appliances without running numerous cords.
  • It’s the easiest and safest way to power appliances like a pump and furnaces.
  • It helps you manage your power usage efficiently.

Some may be wondering if you need a transfer switch for your portable generator. While some people will tell you that you need it, you must understand that it’s dangerous given the reasons above.

When it comes to the installation of the transfer switch, it’s recommended that you leave it to a certified electrician. However, if you’re confident about your do-it-yourself skills, you can follow the guidelines and safely wire a transfer switch to your electrical panel.

Here’s how you can power your house with a transfer switch in 10 steps:

1. Assemble the Things You Need

For installation of the transfer switch system, you’ll need the following:

  • A portable generator: You’ll determine the size of the generator you need for emergencies based on the appliances you wish to power.
  • Transfer switch: A manual transfer switch is practical since you’ll use a portable generator instead of the standby type.
  • Power inlet box: This is a watertight box installed outdoors to connect the generator on the outer end and the transfer switch on the interior end. It should be male (with prongs sticking out the outside) instead of female (with holes you can plug into) so that you don’t use the dangerous male cord.
  • Heavy-duty power cord: A standard length of at least 20 feet would be advisable to complete the connection adequately. Use a power cord with a prong number matching your generator’s.

2. Mount the Transfer Switch Beside the Electrical Panel

Mount the transfer switch right next to the electrical panel to facilitate secure connections.

3. Turn Off the Power in the Electrical Panel

You know you can’t operate your wiring with the electricity on, so this is a reminder. Ensure you turn off the power, so you don’t harm yourself or others.

4. Turn Off the Circuits That You Don’t Need to Power

Having your priority appliances list in hand, distinguish the circuits you need to be powered from those that need to be off. Turn off the less critical circuits.

5. Match the Priority Circuits with the Connections to Your Transfer Switch

Remember to connect the double-pole 240-volt circuits with twin 120-volt circuits. Moreover, ensure that you match the circuits with the required amperage.

Always balance your loads by dividing the high-wattage devices to the far left and right parts of the transfer switch. For instance, place the air compressor on the left if your fridge is on the right end of the circuit.

6. Select a Fitting Knockout Hole and Connect

Check the knockout holes under the electrical panel and choose one that fits the transfer switch conduit. Remove the knockout and attach the cable to the electrical panel.

7. Insert and Connect the Wires from the Transfer Switch to the Electrical Panel

Using a knockout hole, feed the circuit wires from the transfer switch. Each wire is marked according to the circuit it needs to be fed on, so be careful not to mismatch the circuits.

  • Take the priority circuit and remove the hot wire.
  • Install the red wire from the transfer switch with a matching letter on the circuit breaker.
  • Take the removed power wire and connect it to the matching black wire from the transfer switch with a wire nut.
  • Now go for the next circuit and repeat the process until the end.
  • Ensure that you match all the circuit breaker wires with the transfer switch’s corresponding letters.
  • Keep confirming after you’re done with each circuit.

Also, remember to attach two 120-volt connections from the transfer switch to the 240-volt double-pole breaker in the electrical panel. The 120-volt connections should be next to each other in the transfer switch. You can use a handle tie to connect these.

8. Connect the Neutral and Ground Wires

The transfer switch has one neutral and one ground wire for all the circuits. Locate the white (neutral) and green (ground) wires from the transfer switch through the knockout hole and into the service box.

Take the neutral wire from the transfer switch and attach it to an unoccupied space of the neutral bus bar in the main service panel.

Then, pick the green ground wire and attach it to the open port in the grounding bar. This marks the end of the transfer switch installation. So, cover your service panel box and go to the next step.

9. Connect the Transfer Switch to the Power Inlet Box Outside

Remember the power inlet box? Well, you need that to make a connection between the transfer switch and the generator. If you haven’t installed it already, you need to choose a location far away from your house openings, like doors and windows, to prevent generator fumes from making it into your house. Furthermore, make sure it’s above the ground by about two feet.

Here’s how to install the power inlet box:

  1. Open up the box to reveal the mounting openings for proper installation.
  2. Drill a hole in the wall for the conduit to pass through.
  3. Mount the power inlet box using the screws provided with the unit.
  4. Once the power inlet box is in place, connect it to the transfer switch on the inside.
  5. With the heavy-duty power cord provided, connect the generator to the power inlet box on the outside.

Ensure you hear a click as the power cord locks with the power inlet plug holes. Most cords will come with prongs that have extensions. These extensions are like keys that you twist and lock the cord to ensure a tight connection.

10. Turn the Generator On

After confirming that all connections have been properly made, turn the generator on. Flip the circuits to generator mode one at a time, observing the wattage changes. If the generator is powering all your critical circuits, congratulations, you just powered your house with a portable generator through a transfer switch!

If you do not need the generator yet, turn it off and return to the electrical panel to take the switches back to the utility line. Ensure you don’t plug out any cords while the generator is on.

You can get a visual presentation of how to power a house with a portable generator using a transfer switch in this video:

Note: You void the generator warranty or any other supplies you use by doing this process yourself. Some sellers will ask for electrician details if you have a warranty claim.

Portable Generator Using an Interlock Kit

The alternative for a transfer switch is an interlock kit. The generator interlock kit makes it manually impossible to run electricity through the utility line while the generator is on and vice-versa.

It is a less expensive option than the transfer switch, which is why many people choose it. However, it’s illegal to use in some states, so check before choosing a safe way to run your house using a portable generator.

Here’s how you can power your house using an interlock kit:

1. Collect What You Need

Check the amperage of your generator and confirm the type of plug you have. This will help you match the rest of the supplies according to those of your generator.

Feel free to adjust the things you need according to your particular amperage. You’ll find matching components with the most common amperages in the following list of things you need. They are listed respectively.

You’ll need the following:

  • An interlock kit: Ensure that whichever you buy is UL listed as the National Electric Code NEC requirements state.
  • 50, 30, 20 amp breaker
  • 50, 30, and 20 amp power inlet box
  • 50, 30, 20 amp generator extension cord
  • 8, 10, 12 gauge wire
  • Drill
  • Conduit
  • Conduit glue

2. Find the Best Location on the Wall and Drill a Hole

Go outside and find an isolated wall that connects to your utility room. This will help you connect with the generator easily since it’ll also be isolated. You can use a hammer drill to make the hole since it’s much more manageable. Make sure you measure the hole size according to the conduit’s size, nothing less.

3. Mount the Power Inlet Box Over the Hole

Now, remove the knockout and ensure it’s right over the hole so that it fits. Remove the front cover of the power inlet box and mount the back to the wall using the screws that came with the unit. Make sure you hold it securely so it doesn’t slip and enable a messy job.

4. Connect the Power Inlet with a Conduit

Measure the conduit size you need and cut. Attach it to the power inlet box through the hole in the wall, and after ensuring it fits, glue it for a tight seal.

5. Wire the Power Inlet Plug

Pull the wires through the circuit breaker’s conduit and connect them to the generator inlet plug.

Here’s how to do it:

  1. Attach the white neutral wire to the W terminal.
  2. Put the red wire in the X terminal.
  3. Then, screw the black wire in the Y terminal.
  4. Lastly, screw the green ground wire on the power inlet box, one on the top and the other below it, if you will.

Ensure that you’ve tightened the wire enough before securing the plug body back into place. After you’re sure everything is connected correctly, push the wires inside to be ready for the next step.

6. Open the Circuit Breaker and Bring the Wires In

Turn off the branch circuit breakers one by one and, finally, the main breaker. Test all the circuit breakers to ensure they aren’t registering any voltage. Unscrew the panel cover, remove a knockout, and attach the conduit. Pull the wires through the conduit so they can all be seen in the box.

7. Remove Some Breakers for Interlock Kit Space

For the interlock kit to work, it’ll require the place near the main breaker to be free. This is because you’ll be installing the generator breaker and initiating the mechanical advantages of interlocking

Depending on the size of your interlock kit, you might have to remove one or two circuit breakers to another position.

8. Put the Generator Circuit Breaker in the Open Space

Secure the new circuit breaker. Screw the red and black terminals on each side of the circuit breaker. Take the white wire and attach it to the bond rail while the black connects to the ground rail.

After you confirm that everything has gone to the right place, use the retaining bracket to secure the circuit breaker in its place.

9. Drill the Holes for the Interlock Kit

Read the instructions carefully and turn the cover over. Using the template, drill the holes, and finish them according to the size written in the manual.

Then, flip over the cover and fit the sliding bolts for the flexibility of the interlock. Put the cover back in place without turning any breaker on. Confirm whether the interlock is moving properly; only one breaker can be turned on at a time, the main or the generator.

10. Operate

Here’s the fun part. After turning the main breaker off, ensure you’ve connected everything from the generator. Then, do the following:

  • Turn the main generator breaker on.
  • Turn the other breakers on, pausing for a few seconds after each flip. This is to help in distributing the starting load.
  • Ensure that you have made your generator sizing calculations and decided which appliances you will power. This is to help you avoid overload and allow a seamless operation even during a power outage.

Transfer Switch vs. Interlock Kit: Which One Should You Choose?

In electricity chat rooms, you’ll find heated conversations about the transfer and interlock switch. Many of you might be wondering which one you should choose, so we created a chart of the main differences you should know about how to power a house using a portable generator.

Here are the pros and cons of the transfer switch and the interlock kit:

Transfer Switch Interlock kit
They are legal They are illegal in some states
It provides you with a seamless process of powering critical circuits You can overload the generator if the priority circuits aren’t isolated
Averagely expensive Less costly
A transfer kit is applicable for any circuit breaker, new and old For older circuit breakers, a transfer kit may be unavailable
It isn’t versatile when it comes to changing circuits Flexible in changing circuits
Limits you to up to 10 circuits It allows you to power anything you want according to your generator’s wattage.

At the end of the day, whatever choice you make, consider involving a licensed electrician in the installation. The above are mere guidelines to safely power your house instead of using the generator directly. If you take installation matters into your own hands, you risk endangering yourself and others, plus you’ll be voiding some of your warranties.

Generator Sizing Tips

You need to size your generator early enough to determine the best for your home. This could be whether you use the interlock or transfer kit to power your house. Sizing the generator helps you know the generator to get and the circuits to isolate.

Determine the Appliances You Want to Power

When using a portable generator, you must ensure you don’t overload it. This means that you might only be able to power the main electrical appliances in your home.

The best way to determine the devices you’ll use in the case of a power outage is to conduct an energy audit beforehand. For instance, if you use well water, that might go on your priority list. The fridge and heater might also take priority, among others.

A high-watt portable generator typically can power most priority appliances in an average American home. According to the Energy Information Administration (EIA), an average US household consumes 11000kWh annually. This comes to 83kWh per month.

That’s a lot of power, so instead of using the estimated numbers, use your priority appliance list to determine the generator size you need.

Determine Generator Size

You have your list; it’s time to write the wattage according to the values you see on them. If you don’t see wattage, you might see voltage and amperage. In that case, use the following calculation to get their wattage:

Amperage (A) x Voltage (V) = Wattage (W)

After listing the wattage of each appliance, you need to calculate the total and multiply by 1.25. Starting watts are usually higher than running watts, so if you use the device wattage as your reference point, you’ll overload your generator.

If, for instance, you’re running an air compressor with a wattage of 2000W, it’s likely to start using 4000W before decreasing its usage to 2000W. So, multiplying by 1.25 adds a 25 percent allowance to contain the starting watts.

If you haven’t bought the generator yet, this is the guideline you can use to get one that fits your house needs. However, if you already have one, you can determine the essential appliances for a safe load.

Portable Generator Safety Tips You Must Know

According to Consumer Reports, 900+ people died due to carbon monoxide poisoning, and thousands got injured using portable generators from 2005 to 2017.

Here are some safety tips for portable generators you need to know:

  • Don’t use a male plug.

The male plug is hazardous, yet many people use it with the generator during a power outage. Some electricians refer to it as the suicide cord or the widow maker. That should tell you a great deal about it. When you use this plug, it’ll be like you’re using a naked wire. When it comes into contact with anyone, it’ll shock them. When it comes into contact with some materials, it could cause a fire.

When you use the male plug to power your devices, there’ll be a flow of electricity back and forth, and this could fry your appliances or cause an electric fire from somewhere in the connections.

These plugs aren’t supposed to be on the market because they are illegal. You’ll never find a UL listing on any male plug, and no reputable electrician can use one because they might lose their license. If you still use the male plug, consider installing a transfer switch or interlock kit as soon as possible. It’s just not worth the danger.

The following video explains all the dangers of using a male plug:

  • Put the generator 20 feet away from your home.

Carbon monoxide poisoning will likely happen when you use a portable generator:

  • Indoors
  • In a semi-ventilated space
  • Close to you
  • With the exhaust pipe directed at you

In worst-case scenarios where you have to use a portable generator in the above conditions, get a reliable carbon monoxide detector to notify you in case the levels become dangerous.

Many generator user manuals state that you shouldn’t use the machines in the rain, snow, and other moisture-packed conditions. Yet you find yourself needing them during these conditions most. So, why do they warn you?

One reason is your safety, and the other is for the protection of the generator itself. Generators typically produce high voltage, and if coupled with water, it can cause electrocution. Moreover, if some water enters the generator’s intimate parts, it can short circuit and damage it for good.

So what’s the solution? You can keep your and the generator safe by using a waterproof cover. If you have a well-ventilated shed 20 feet from your house, you can put the generator there to ensure your safety.

When fueling a portable generator, you need to take precautions, such as:

  • Turn off and wait for the generator to cool before fueling to prevent ignition once the fuel hits the hot generator.
  • Do not fuel while smoking or when near any flame.
  • Store fuel in a well-ventilated space with a generator fuel-approved container.
  • Store your generator fuel in a low-traffic area.
  • Keep a fire extinguisher close to your generator operating space and be ready to use it when it arises.


The best part about using a transfer switch or interlock device to power your house is that you can efficiently use the portable generator during a power outage and unplug it for other outdoor activities when the need arises.

So, whatever you choose, know that you can power your house with a portable generator. Remember the generator sizing and safety tips when a power outage occurs.

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