Home Generator Installation: What to Know Before You Buy

Power outages in California can last hours or days - from wildfire-related PSPS (Public Safety Power Shutoffs) events to winter storms and grid issues. A home generator can keep critical systems running when utility power goes out. But buying one and installing it properly are two different things, and the installation side is where most homeowners run into surprises. This guide covers what to know before you commit.

Standby Generators vs. Portable Generators

The biggest decision is standby vs. portable.

Portable generators run on gasoline or propane, are stored in your garage or shed, and need to be manually started and connected when power goes out. They typically range from 3,000 to 10,000 watts. Cost for the unit runs from around $500 to $2,500 depending on size and brand. They cannot be connected directly to your home wiring without a transfer switch - running power from a portable generator into your panel without a transfer switch (called back-feeding) is extremely dangerous to utility workers and is illegal.

Standby generators are permanently installed outside the home, connect to a dedicated fuel supply (natural gas or propane), and start automatically within seconds of an outage. They typically range from 7,500 watts to 22 kilowatts or more for whole-home coverage. They are significantly more expensive - the unit plus installation often runs somewhere in the range of $5,000 to $15,000 or more depending on size and the complexity of the installation.

For most California homeowners who primarily want to run critical circuits during a PSPS event, a portable generator with a proper transfer switch is often the more practical and affordable option. For those who want whole-home coverage without any manual intervention, a standby generator makes more sense.

What a Transfer Switch Does and Why You Need One

A transfer switch is the piece of equipment that safely disconnects your home from the utility grid before connecting it to generator power. Without one, generator power can back-feed into utility lines and electrocute workers doing repairs.

For portable generators, you have two options:

Manual transfer switch. Installed in your electrical panel, it lets you manually flip specific circuits to generator power. Installation typically runs around $400 to $800 in labor plus equipment, depending on how many circuits you want covered.

Interlock kit. A mechanical device that prevents the main breaker and a generator breaker from both being on at the same time. Simpler than a transfer switch, lower cost, but covers all circuits at once which means your generator needs to be large enough to handle whatever you run.

For standby generators, an automatic transfer switch (ATS) is always included and is installed as part of the job.

What Circuits to Prioritize

Most portable generators cannot power an entire home. Thinking through priorities before installation helps you size both the generator and the transfer switch correctly. Common priority circuits include:

• Refrigerator and freezer (critical for food safety)
• Medical equipment (CPAP, nebulizers, home oxygen)
• Furnace or HVAC blower (even gas furnaces need electricity to run the blower)
• Well pump (if on a private well)
• A few lighting circuits
• One or two outlet circuits for phone charging and small appliances

A 7,500-watt portable generator can typically handle most of these if you are selective about what runs simultaneously. Running central air conditioning requires significantly more capacity.

Permits and Code Requirements in California

Generator installation in California almost always requires a permit. Permanently installed standby generators require electrical permits and, in many cases, mechanical and gas permits as well. Some jurisdictions also have noise ordinances that affect where a standby generator can be placed.

In Los Angeles, San Diego, Sacramento, and Riverside, the permit and inspection process for a standby generator typically adds around $200 to $600 to the project cost, but it also ensures the installation is inspected for safety.

Portable generator transfer switches also require permits in most California jurisdictions. This is often skipped by homeowners, but an unpermitted transfer switch can create problems if you ever sell the home or make an insurance claim.

Fuel Considerations

Natural gas is the most convenient fuel for standby generators. You do not have to store fuel, and the supply is generally reliable. The generator connects to the home's existing gas line, though the line may need to be upsized depending on the generator's fuel demand.

Propane is used when natural gas is not available. Propane requires a storage tank, which needs to be sized appropriately - a large standby generator can consume 2 to 3 gallons per hour under load. A 250-gallon tank might provide only 3 to 4 days of continuous operation.

Gasoline (portable generators) is widely available but degrades in storage. Fuel stabilizer extends shelf life to around 12 months. Never run a gasoline generator indoors or in an attached garage - carbon monoxide is the leading cause of generator-related deaths.

Sizing the Generator

Generator sizing is based on wattage. Add up the running wattage of everything you want to power simultaneously, then add extra for startup surges (motors can pull 2 to 3 times their running wattage at startup). An undersized generator will either stall or fail to start the load.

For whole-home standby generators, a licensed electrician or the generator installer typically conducts a load calculation. Common whole-home sizes in California single-family homes range from 14 kilowatts for a modest home with gas appliances to 22 kilowatts or more for all-electric homes or homes with HVAC-heavy loads.

Installation Costs to Expect

In California, standby generator installation costs vary widely. Common cost ranges:

• Generator unit (14 to 20 kW): often around $3,500 to $7,000
• Installation labor, transfer switch, gas line work, electrical permit, and inspection: often around $2,500 to $6,000
• Total installed cost for a mid-size standby generator: often somewhere in the range of $7,000 to $13,000

These figures can run higher in areas with high labor costs (Los Angeles in particular) or if the project requires significant trenching, a new gas meter, or panel work.

For a portable generator setup with a manual transfer switch, total cost is usually much lower - often around $1,500 to $3,500 for a quality generator plus professional transfer switch installation.

What to Verify When Hiring a Contractor

For standby generator installation, look for a contractor who is:

• Licensed as an electrical contractor (C-10) in California
• Also licensed or working with a licensed plumber or HVAC contractor for gas line work if needed
• Familiar with your local jurisdiction's permit requirements

Some generator dealers (Generac, Kohler, Cummins) have certified dealer networks that handle permit, installation, and warranty service as a package. This can simplify the process but does not always represent the lowest price.

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Sources and editorial notes

Prices and permit requirements vary by location, property, equipment, and scope. Treat price ranges as planning estimates and confirm current requirements with the relevant authority and contractor.

• California Contractors State License Board - when a contractor license is required
• US Department of Energy - Energy Saver
• US Consumer Product Safety Commission - home safety

Related guides

• What to Do After a Power Outage (Home Safety Checklist)
• How to Run Power to a Detached Garage or Workshop
• Dishwasher Installation Requirements: Plumbing, Power, and Space

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