Solar + Battery: Keep Lights On During CA Outages

California homeowners dealt with more than 800 Public Safety Power Shutoff (PSPS) events between 2019 and 2024, according to the California Public Utilities Commission. If you have solar panels on your roof but no battery, your system shuts off the moment the grid goes down. That means your panels sit idle while your food spoils and your family sits in the dark. Adding battery storage changes the equation entirely, turning your solar investment into a reliable backup power source that works when you need it most.

Why Do Solar Panels Shut Down During Power Outages?

Most homeowners assume their solar panels will keep the lights on when the grid fails. The reality is different. Standard grid-tied solar systems are required by law to shut down during outages through a process called anti-islanding protection.

Here is why: when utility crews work on downed power lines, they need to know the lines are dead. If your solar panels kept pushing electricity onto the grid, workers could be electrocuted. The National Electrical Code (NEC) requires every grid-tied inverter to detect a grid outage and disconnect within two seconds.

This safety feature protects lives, but it also means your 8kW rooftop solar system produces zero watts during an outage. You have panels generating potential electricity, an inverter that refuses to convert it, and a dark house. The only way around this is adding a battery system that can “island” your home, disconnecting it from the grid and creating a self-contained power loop.

How Solar Battery Backup Keeps Your Home Running

A solar battery backup system adds a critical missing piece to your solar setup. When the grid goes down, the battery’s inverter automatically disconnects your home from utility lines and switches to stored power. This transition happens in milliseconds, so fast that most homeowners never notice the grid went out.

During daylight hours, your solar panels continue generating electricity. But instead of feeding it to the dead grid, the energy routes through the battery system to power your home and recharge the battery simultaneously. This “islanding” capability means you can ride out multi-day outages as long as the sun keeps shining.

The battery handles overnight power needs. A properly sized system stores enough energy during the day to keep essential loads running through the night, then refills from solar the next morning. It creates a self-sustaining cycle that no generator can match without constant fuel deliveries.

One detail worth knowing: not all battery systems support solar recharging during an outage. Some older or budget models can discharge stored energy but cannot accept new solar input while islanded. When shopping for a battery, confirm that the system supports “solar charging in backup mode” so your panels actively contribute during extended outages.

What Can a Solar Battery Power During an Outage?

Battery backup systems are typically configured in one of two ways, depending on your budget and power needs.

Essential Loads Backup

This is the most common setup. A dedicated subpanel powers your most important circuits:

• Refrigerator and freezer (preventing hundreds of dollars in food loss)
• Wi-Fi router and modem (maintaining communication and remote work)
• Lighting in key rooms
• Phone and device charging
• Garage door opener
• Medical equipment if needed

A single Tesla Powerwall (13.5 kWh usable capacity) can keep these essential loads running for 12 to 24 hours on a full charge, depending on consumption. With solar recharging during the day, that runtime extends indefinitely for essential circuits.

Whole-Home Backup

For homeowners who want to keep air conditioning, cooking appliances, and multiple rooms fully operational, a two- or three-battery system provides enough capacity to cover most household loads. A whole-home backup requires careful load planning with your installer to prevent overloading the system during peak demand moments like HVAC startup.

Central Valley summers regularly push temperatures above 105 degrees, making air conditioning a safety concern rather than a comfort preference. If keeping your home cool during a summer outage is a priority, plan for at least two batteries and discuss HVAC load management strategies with your installer during the design phase.

Sizing Your Battery for California Outage Scenarios

The right battery size depends on three factors: what you want to power, how long outages typically last in your area, and how much solar generation your panels produce daily.

Step 1: Calculate Your Essential Load

List every appliance and circuit you need during an outage. Add up the wattage for each. A typical California home’s essential load runs between 3,000 and 5,000 watts, or about 20 to 30 kWh per day.

Step 2: Factor in Outage Duration

PSPS events in Central and Southern California usually last 24 to 48 hours, though some have stretched to five days. PG&E and SCE both publish outage maps and PSPS event histories for their service areas. If you live in a high-fire-risk zone, plan for longer outage windows.

Step 3: Match Battery Capacity to Your Needs

Your solar panel system size also matters. A 6kW system generates roughly 24 to 30 kWh on a sunny California day, enough to power essential loads and fully recharge a single battery. Larger systems paired with multiple batteries can keep an entire household comfortable through extended outages.

How Much Does Solar + Battery Storage Cost?

The cost of adding battery storage to an existing solar system or installing both together varies based on battery brand, capacity, and installation complexity.

For a single-battery system (13-16 kWh), expect to pay between $12,000 and $18,000 before incentives. A two-battery whole-home setup typically falls in the $22,000 to $32,000 range before incentives.

Several incentives reduce this cost significantly:

• Federal Investment Tax Credit (ITC): The 30% federal tax credit applies to battery storage systems when paired with solar, cutting a $15,000 battery cost to roughly $10,500 after the credit.
• California SGIP (Self-Generation Incentive Program): This state rebate offers up to $1,000 per kWh of battery capacity. Homeowners in high-fire-risk areas or low-income qualifying households may receive even higher rebates, sometimes covering up to 100% of battery costs.
• NEM 3.0 Bill Savings: Under California’s current net billing tariff, batteries let you store daytime solar production and use it during expensive evening peak rates (4 PM to 9 PM), saving $20 to $30 per month compared to exporting at low wholesale rates.

Sun Solar Pros offers a solar + battery combo starting at $99 per month with $0 down financing, making backup power accessible without a large upfront investment. This monthly payment often comes in below what homeowners currently pay their utility company.

Tesla Powerwall vs. SunVault: Which Battery Is Right for You?

Sun Solar Pros installs both Tesla Powerwall and SunVault battery systems. Each has strengths depending on your situation.

Both systems provide automatic backup during outages, solar recharging in island mode, and time-of-use rate optimization. Your Solar Educator at Sun Solar Pros can help determine which battery matches your panel brand, electrical setup, and backup goals.

California Power Outages Are Getting More Frequent

If you think power outages are rare, the data tells a different story. California’s grid faces growing pressure from multiple directions:

• Wildfire-related PSPS events: PG&E, SCE, and SDG&E now proactively shut off power during high-wind, low-humidity conditions to prevent wildfires. These shutoffs can affect hundreds of thousands of customers at once and last multiple days.
• Extreme heat events: Summer 2022 pushed California’s grid to the brink, with CAISO issuing Flex Alerts and rotating outages as air conditioning demand exceeded available generation. The state’s growing population and hotter summers mean this strain will increase.
• Aging infrastructure: Much of California’s transmission and distribution grid is decades old. Equipment failures cause unplanned outages that can last hours or days, especially in rural areas of the Central Valley.
• Earthquake risk: A significant seismic event could disrupt grid infrastructure for extended periods, making home-level energy independence a practical safety measure.

For homeowners in Bakersfield, Fresno, Visalia, and throughout the Central Valley, battery storage is becoming less of a luxury and more of a practical necessity.

5 Questions to Ask Before Adding Battery Backup

1. What appliances do I need during an outage? List everything, then prioritize. This determines your battery size and budget.
2. How long do outages last in my area? Check your utility’s outage history. Homeowners in high-fire-risk zones should plan for 48+ hour events.
3. Is my solar system large enough to recharge the battery? Your installer can assess whether your current panel output can keep the battery topped up during multi-day outages.
4. Do I qualify for SGIP rebates? High-fire-risk area designations and income qualifications can dramatically reduce battery costs. Your installer can check eligibility.
5. Can my electrical panel handle a battery? Older homes may need a panel upgrade or subpanel to accommodate battery backup wiring. A site evaluation identifies this upfront.

Why Central Valley Homeowners Choose Sun Solar Pros for Battery Installation

Sun Solar Pros has installed thousands of solar and battery systems across Central and Southern California since 2008. As SunPower’s most award-winning partner with nine consecutive years as Residential Regional Top Producer, the company brings a level of experience that matters when designing a backup power system.

Battery installations require precise electrical work, proper load calculations, and coordination with your utility for interconnection. Sun Solar Pros handles the entire process, from initial assessment through permitting, installation, and activation. The company is also a Tesla Powerwall Certified Installer, meaning their technicians have completed Tesla’s training program for battery system design and installation.

Every project starts with a free home energy assessment where a Solar Educator reviews your electricity usage, outage history, and backup priorities. You receive a custom recommendation with clear pricing, financing options, and a timeline, typically about 12 weeks from contract to activation.

Frequently Asked Questions

Does solar work during a power outage without a battery?

No. Standard grid-tied solar systems shut down during outages due to anti-islanding safety requirements. Your inverter detects the grid outage and disconnects within seconds. Adding a battery with islanding capability is the only way to use solar power during a blackout.

How long will a solar battery last during an outage?

A single 13.5 kWh battery like the Tesla Powerwall can power essential loads (refrigerator, lights, Wi-Fi, phone charging) for 12 to 24 hours on a full charge. With solar panels recharging the battery during the day, essential loads can run indefinitely as long as there is sufficient sunlight.

Can I add a battery to my existing solar panel system?

Yes. Batteries like the Tesla Powerwall are designed to retrofit onto existing residential solar installations. Your installer will evaluate your current inverter, electrical panel, and solar output to confirm compatibility and recommend the right battery size.

Is a solar battery better than a gas generator for backup power?

For most California homeowners, yes. Solar batteries operate silently, produce no emissions, require no fuel deliveries, and recharge automatically from your panels. Generators require fuel storage, produce carbon monoxide (requiring outdoor placement), and need regular maintenance. Batteries also qualify for the 30% federal tax credit and SGIP rebates, while generators do not.

How much does a solar battery cost in California?

A single-battery system typically costs $12,000 to $18,000 before incentives. After the 30% federal tax credit and any SGIP rebates, the net cost can drop to $7,000 to $12,000. Sun Solar Pros offers financing starting at $99 per month with $0 down.