When the power goes out in San Diego—whether from a storm or an SDG&E Public Safety Power Shutoff (PSPS)—having a generator is a smart move. But connecting that generator to your home’s electrical system isn’t as simple as running an extension cord. You need a safe, code-compliant way to power your home without endangering utility workers, and that means choosing between a generator interlock kit and a transfer switch.
What an interlock kit actually is (and isn’t)
A generator interlock kit is a simple, effective, and affordable mechanical device. It’s a small metal plate that slides over your electrical panel’s cover. Its one and only job is to prevent the main breaker (from the utility grid) and the generator backfeed breaker from being turned on at the same time. You physically cannot have both active simultaneously.
This is critical because it prevents “backfeeding.” Backfeeding happens when electricity from your generator travels out of your house, through the transformer, and onto the utility lines. This can create a deadly hazard for SDG&E lineworkers who think the lines are de-energized and are working to restore power. The National Electrical Code (NEC) has strict rules under Article 702 to prevent this, and a properly installed interlock kit is a recognized, safe method.
An interlock kit allows you to use your existing breaker panel to distribute power. Once the generator is running and the main breaker is off, you can turn on individual circuit breakers just like you normally would. You’ll have to manually manage the electrical load to avoid overloading your portable generator, but it gives you the flexibility to power any circuit in your home, as long as your generator can handle it. It’s a straightforward solution designed for use with a portable generator.
Manual transfer switch: how it works and what it costs
A manual transfer switch for a generator is a more structured approach to powering your home during an outage. Instead of using your main panel to distribute power, a transfer switch is a separate, smaller electrical panel (a subpanel) installed next to your main one.
Here’s how it works: a licensed electrician identifies the most essential circuits in your home—things like your refrigerator, furnace fan, a few lights, and your internet router—and moves them from your main panel to the new transfer switch. During an outage, you start your portable generator, plug it into an inlet box, and then flip a single master switch on the transfer switch. This action completely disconnects those chosen circuits from the utility grid and connects them to the generator feed.
The primary benefit is simplicity during an outage. There’s no need to flip individual breakers in the main panel. You know exactly which circuits will be powered, and it’s harder to accidentally overload your generator. It’s a very safe and foolproof method. The downside is that you’re limited to only the circuits you pre-selected during installation. If you suddenly need to power your home office computer but it wasn’t wired into the switch, you’re out of luck.
Automatic transfer switch for whole-home standby
For homeowners who want seamless, hands-off power restoration, the automatic transfer switch (ATS) is the only way to go. This device is the brain of a whole-home standby generator system. An ATS constantly monitors the power coming from the utility grid.
The moment it detects an outage from SDG&E, it triggers a sequence of events. First, it isolates your home’s entire electrical system from the grid. Then, it signals your standby generator to start up. Once the generator is running at the correct speed and voltage, the ATS automatically transfers your home’s entire electrical load to the generator. The whole process takes about 10 to 20 seconds, often so quickly that you’ll only notice a brief flicker of the lights.
When utility power is restored, the ATS senses it, transfers the load back to the grid, lets the generator run for a short cool-down period, and then shuts it off. It’s the ultimate convenience, ensuring your home stays powered whether you’re there or away on vacation. Naturally, this level of automation and power comes at a higher cost and is specifically designed for permanently installed standby generators, not portable ones. For many, the peace of mind offered by a complete whole-house generator installation is well worth the investment.
Code, permits, and SDG&E inspection requirements
In San Diego County, installing any device that connects a generator to your home’s wiring is not a DIY project. Both a generator interlock kit and any type of transfer switch legally require an electrical permit from your local city or county building department. This isn’t just about bureaucracy; it’s about life safety.
The installation must comply with the NEC to ensure it’s done correctly and safely, preventing the risk of fire or electrocution. A licensed electrician will ensure the wiring is the correct gauge, the breakers are properly sized, and the entire system is grounded correctly. After the work is complete, a city or county inspector will need to sign off on the installation. This final inspection is what closes the permit and certifies that the work is safe and up to code.
For some installations, particularly larger standby systems with an automatic transfer switch, SDG&E may also need to be involved or notified. This ensures that the system is compatible with their grid and meets all utility requirements for safe interconnection. Trying to bypass the permitting process can lead to fines, difficulty selling your home, and denial of insurance claims if something goes wrong.
PSPS scenarios: which fits portable vs. standby
San Diego residents are becoming increasingly familiar with SDG&E’s Public Safety Power Shutoffs. The right generator connection depends heavily on what kind of generator you have and what you want to achieve during a PSPS event. Our complete generator guide for PSPS shutoffs covers this in more detail, but here’s a quick breakdown.
For Portable Generators
If you have a portable generator (typically 5,000 to 10,000 watts), your choice is between an interlock kit and a manual transfer switch.
- Generator Interlock Kit: This is the most flexible and cost-effective option for a portable generator. It lets you power any circuit in your home, as long as you manually manage the load to stay within your generator’s capacity. During a PSPS, you can choose to run the fridge and freezer for a few hours, then switch to powering your home office or a window AC unit.
- Manual Transfer Switch: This is the “simpler in a crisis” option. You pre-wire 6-10 essential circuits. When the power goes out, you just flip one switch. It’s less flexible but removes the guesswork and the risk of overloading the generator.
For Standby Generators
If you’re investing in a permanent standby generator, an automatic transfer switch isn’t just an option—it’s a requirement. The two are sold and installed as a complete system. This setup provides automatic, whole-home power that keeps everything running, from the central air conditioning to the security system, without you having to lift a finger. For extended outages, this is the most comfortable and reliable solution.
Cost comparison for a typical San Diego install
The cost to connect a generator to your home in San Diego varies based on the method, the complexity of your electrical panel, and labor. Here are some general price ranges you can expect for a professional, permitted installation.
-
Generator Interlock Kit Installation: This is the most budget-friendly option. A typical installation, including the kit itself, a new 30-amp or 50-amp double-pole breaker, a heavy-duty power inlet box on an exterior wall, and all labor and permitting, generally falls between $900 and $1,500. The main variables are the brand of your electrical panel and the distance from the panel to the new inlet box.
-
Manual Transfer Switch Installation: This is the mid-range option. The cost is higher due to the extra equipment (the switch/subpanel itself) and the more intensive labor required to reroute several of your home’s circuits into the new switch. Expect the total cost to be between $1,500 and $3,000. The final price depends on how many circuits you want to connect.
-
Automatic Transfer Switch Installation: This is part of a larger project and represents the premium solution. The ATS unit itself can cost over $1,000, and the installation is complex. When bundled with a full standby generator installation service, the ATS portion of the project contributes significantly to a total project cost that often starts around $10,000 and can go up depending on the size of the generator.
When to call us
Choosing and installing the right generator connection is a critical safety decision. This work involves direct interaction with your home’s main electrical service, requires a deep understanding of the electrical code, and must be permitted and inspected. For the safety of your family and utility workers, this is a job that should only be performed by a qualified, licensed, and insured electrician.
If you’re ready to prepare your San Diego home for the next power outage, we can help you select and install the perfect solution for your needs and budget. Call us at (858) 925-5546 for a same-day estimate.