When the power goes out, a backup generator can offer peace of mind and comfort by keeping your essential systems running. Connecting a generator to your house safely and effectively, though, involves more than just plugging in a few extension cords. This guide will walk you through the proper steps to connect a generator to your home’s electrical system for reliable backup power during utility outages. Plus, master electrician Heath Eastman helps a homeowner set theirs up correctly in the video above.
Generator Safety Basics
As handy as they are, generators do come with a few safety considerations. Careful setup helps protect your home and family. Here are key safety points:
- Direction: Point the exhaust away from windows and doors.
- Distance: Place the generator at least 10 feet away from your home.
- Foundation: Place the generator on a level, stable surface.
- Ventilation: Avoid any spot where carbon monoxide could build up.
Pro Tip: Scott, a TOH electrician, stresses the importance of proper placement: “We need to stay 5 ft away from any window or door because of combustion.” For standby generators, he adds that you need the same 5-foot clearance from anything combustible, including your home’s siding.
Carbon monoxide poisoning is a serious risk associated with improper generator use. Never run a generator inside an attached garage or close to windows, as exhaust fumes can seep into your home. Always use carbon monoxide detectors in your house when operating a generator.
TOH plumbing and heating expert Richard Trethewi shared a harrowing story that underscores why CO detectors are non-negotiable: His pregnant niece was home feeling queasy, not realizing carbon monoxide was filling the house. When her husband arrived and replaced the CO detector’s low battery, “the CO detector just gets crazy. They immediately get out of the house and the people came and they found out that the house was 100 times more CO and it could have killed both of them.” Richard called it brutal — and a reminder that anytime you have combustion, you have the potential for deadly CO buildup.
Choosing the Right Generator Connection Method
When connecting a generator to your home’s electrical system, you’ll typically choose between a transfer switch and a mechanical interlock. Here’s a quick look at each option:
| Feature | Transfer Switch | Mechanical Interlock |
| Installation | Between panel and inlet | In the electrical panel |
| Circuit Selection | Preselected | Flexible; any circuit |
| Ease of Use | Simpler; fewer monitoring needs | Requires manual monitoring |
| Safety | Limits overload risk | Higher risk of overload if not managed carefully |
| Cost | Generally higher | Generally lower |
Transfer Switch
A transfer switch is a device installed between your electrical panel and the power inlet that allows you to power specific circuits in your home. This option is ideal for those who want a straightforward, preselected setup. A transfer switch limits the number of circuits the generator can power, helping to avoid overloads.
Pro Tip: Scott, a TOH electrician, explains that a transfer switch is essentially a safety mechanism: “There’s no way the street power will actually collide with the generator power and cause an issue.” He adds that while it forces you to preselect your critical circuits, “once you pick them, they’re there and you’re good to go and that’s it. It’s nice and simple, but you are limited to those circuits.”
Mechanical Interlock
A mechanical interlock fits directly in your electrical panel. It provides more flexibility, allowing you to power any circuit in your home. However, it also requires more attention to prevent overloading. This option works best if you’re comfortable managing power use manually.
Installing a Power Inlet Box for Your Generator
A power inlet box creates a safe connection point for your generator on the outside of your home. There are two main types of power inlet boxes:
- Front-mount inlets: More exposed to the elements.
- Bottom-mount inlets: Offer better weather protection and are generally preferred.
Choose a spot that’s easy to reach from your generator location and doesn’t block outdoor features like deck stairs. Position it close to your electrical panel to simplify wiring.
Generator Installation Process
While we recommend having a licensed electrician perform the installation, understanding the process can help you make informed decisions as a homeowner. Here’s an overview of the steps involved if you choose the more user-friendly transfer switch option, as Eastman installs in the video:
- Disconnect utility power: The local utility company must shut off power to your panel and remove the meter.
- Mount the transfer switch: Install a mounting board near your electrical panel and secure the transfer switch to it.
- Connect to the electrical panel: Run flexible conduit from the transfer switch to the panel and connect individual circuits.
- Install the power inlet box: Choose an appropriate location on the exterior of your home and run conduit to connect it to the transfer switch.
- Test the system: Before reconnecting utility power, test the generator and transfer switch for proper operation.
Using Your Generator Safely
Once your generator is installed, you’re ready for any power outage. Here’s what to do:
- Set up the generator: Move it to its designated outdoor spot.
- Connect the power cord: Attach the power cord from the inlet box to the generator.
- Start the generator: Follow the manufacturer’s instructions.
- Activate power: Use the transfer switch to direct power to selected circuits in your home.
If you’re using a mechanical interlock instead, be careful to monitor the load closely. Start with essential appliances and add others gradually to avoid overload. Know your generator’s load capacity and be familiar with emergency shutdown steps.
Pro Tip: Heath, a licensed electrician featured on This Old House, advises a careful startup sequence: “When the power goes out, you turn everything off, turn the generator on, make your switch. Now start turning things back on one at a time. So you get your water, your furnace, refrigerator, lighter too, even a few other receptacles, possibly a TV.” He notes the generator “can run the bulk of the house because at any given point, you’re not using that much power.”
What to Avoid: Heath cautions homeowners to keep high-draw appliances off the generator circuit: “What you want to keep away from though is maybe the electric oven, your dryer, bigger items, your central air conditioner.” If you overload it? “The generator will actually shut down.”
Maintaining Your Generator
Regular upkeep keeps your generator ready for any emergency. Perform regular oil changes as recommended by the manufacturer, and check and replace air filters as needed.
We recommend testing the generator monthly to make sure it starts and runs properly. Double-check all connections between the generator, power inlet box, and transfer switch and inspect and clean the spark plugs. Be sure to keep spare parts on hand, such as oil filters, spark plugs, and fuel.
