Here is a fact most solar homeowners learn the hard way: a standard solar system will not power your house during a grid outage. Not even if the sun is shining. The same panels that run your air conditioner all summer will go completely dark the moment your utility’s power goes out, because grid-tied systems are required by law to shut down automatically to protect utility workers on the lines. If you have ever had solar and still lost power during a storm or a PG&E Public Safety Power Shutoff, this is exactly why.
A solar battery backup system for home changes that equation entirely. Paired with your existing or new solar panels, a home battery stores the energy your panels generate during the day and deploys it automatically the moment grid power disappears. The switchover typically takes less than a second. Most homeowners never notice the transition.
This guide explains how these systems work, what they can and cannot power, what the real costs look like in 2025, and what California incentives are available right now to help Fresno-area homeowners offset the investment.
How a Solar Battery Backup System for Home Actually Works
When solar panels generate electricity, they produce direct current (DC) power. Your home runs on alternating current (AC). An inverter converts between these two forms, and in a battery-equipped system, that same inverter also manages the flow of energy between your panels, the battery, the grid, and your home’s circuits.
During a normal day with no outage, the system works in a simple priority order: your panels first power your home’s current needs, then charge the battery with any surplus, then send whatever remains to the grid for net metering credits. At night, or when the sun is not producing enough, your home draws from the battery first before pulling from the grid.
When the grid goes down, the system detects the outage and activates what is called island mode. An automatic transfer switch disconnects your home from the grid, preventing backfeed, and the battery takes over within milliseconds. If the sun is still shining, your panels continue charging the battery during the outage, which can extend backup power indefinitely on sunny days. According to Aurora Solar, this cycle can repeat day after day as long as sunlight is available, making a solar-plus-battery setup far more resilient than a generator for extended outages.
What a Home Battery Can Actually Power and for How Long
Capacity determines runtime. Most residential batteries on the market today fall between 10 and 20 kWh of usable storage. A single Tesla Powerwall 3 holds 13.5 kWh. A FranklinWH aPower 2 holds 13.6 kWh. Systems can be stacked with multiple batteries for greater capacity.
What that capacity can power depends entirely on how many circuits you are running. A 10 kWh battery running only your refrigerator, a few lights, and phone chargers can last 24 hours or more. Add a central air conditioner, and that same battery may cover 4 to 6 hours. This is why most battery installations include a critical load panel, a sub-panel that isolates your most important circuits and dedicates battery power to those first, rather than trying to power the whole house indiscriminately.
Common critical loads homeowners prioritize:
- Refrigerator and freezer
- Lighting in key rooms
- Medical equipment (CPAP, oxygen concentrators)
- Wi-Fi router and phone charging
- Select outlets in living areas
- Well pump (requires higher-capacity setup)
Whole-home backup, meaning every circuit in the house, is possible but typically requires multiple batteries and a larger investment. Most households find that a critical-load setup covers everything that actually matters during an outage at a significantly lower cost.
What a Solar Battery Backup System for Home Costs in 2025
Nationally, turnkey home battery storage averages $1,500 to $2,000 per usable kilowatt-hour (kWh) installed in 2025, according to PPM Solar. For a single 13.5 kWh system like the Powerwall 3, that puts the installed cost in the $15,000 to $20,000 range before incentives. That figure includes the battery unit, backup gateway, automatic transfer switch, critical load panel wiring, permits, labor, and inspection.
The before-incentives number is the one that stops most homeowners. The after-incentives number is often dramatically different, particularly in California.
The federal Investment Tax Credit (ITC) applies to battery storage systems at 30%, whether the battery is installed alongside new solar or added to an existing system. On a $15,000 installation, that is a $4,500 reduction in federal tax liability. The credit is claimed on your federal return in the year the system is installed.
The California SGIP Rebate Can Cut Costs Even Further
California’s Self-Generation Incentive Program (SGIP), administered by the California Public Utilities Commission (CPUC), offers cash rebates to residential customers who install qualifying battery storage systems. Pacific Solar customers in PG&E territory are eligible to apply.
For general market residential customers, SGIP rebates typically run $150 to $300 per kWh of storage. On a 13.5 kWh system, that is an additional $2,000 to $4,000 back. For lower-income households, the numbers are substantially higher.
In June 2025, California launched the Residential Solar and Storage Equity (RSSE) budget, a $280 million program offering up to $1,100 per kWh for storage plus $3,100 per kW for solar for households at or below 80% of area median income. For qualifying families, the combined SGIP rebate and federal ITC can make an entire solar-plus-storage system cost nothing out of pocket, according to the California Energy Initiative.
SGIP budgets are finite and some utility territories have reached waitlist status. Homeowners considering a battery system should apply as early as possible rather than waiting for prices to drop further.
Solar Battery Backup vs. a Standby Generator: Which Makes More Sense
The most common comparison homeowners make is between a solar battery and a natural gas standby generator. Both provide backup power, but they work differently and fit different priorities.
A standby generator runs on fuel and can produce power indefinitely as long as the gas supply holds. It handles large loads like whole-home HVAC without the capacity concerns of a battery. The tradeoffs are noise, exhaust emissions, fuel cost, and mechanical maintenance. A solar battery backup system for home operates silently, produces no emissions, has no fuel cost once installed, and requires virtually no maintenance. Its limitation is capacity: once the battery is depleted and the sun is not shining, backup power ends until the grid or sun returns.
For most Central Valley homeowners dealing with Public Safety Power Shutoffs, which are typically planned, daytime events in clear weather, a solar-plus-battery system handles the scenario better than a generator. The sun is shining precisely when the shutoffs occur, which means the battery charges throughout the outage and can provide power well into the evening.
Frequently Asked Questions About Solar Battery Backup Systems for Home
Do I need solar panels to install a home battery backup system?
No. A battery can be charged from the grid without solar panels. However, pairing a battery with solar panels significantly improves the value: it lowers your electricity costs during normal operation, qualifies you for the federal ITC at 30%, and allows the battery to recharge during an outage rather than depending solely on stored capacity.
How long will a home battery last during a power outage?
Runtime depends on battery capacity and how much power your home is drawing. A single 13.5 kWh battery running only essential loads (refrigerator, lights, Wi-Fi, phone charging) can last 12 to 24 hours. If your solar panels are producing during the outage, they will extend that runtime by continuously recharging the battery throughout the day.
Are solar battery backups worth it in California?
For most Central Valley homeowners, yes. PG&E’s rising rates and regular Public Safety Power Shutoffs make backup power genuinely valuable, not just a convenience. When you factor in the 30% federal ITC and California’s SGIP rebate, the net cost of a battery system is significantly lower than the sticker price, and the payback period shortens considerably for homes already producing solar energy.
Can a solar battery backup power my air conditioner?
Central air conditioning is one of the higher-draw appliances in any home, typically pulling 3 to 5 kW during operation. A single battery can run a central AC unit, but it will deplete faster than when powering lighter loads. Many homeowners with battery backup choose to set the AC thermostat higher during an outage to preserve battery life, or they run a smaller portable AC unit on a critical load circuit instead.
Will my solar battery qualify for the federal tax credit?
Yes, as long as it meets IRS capacity requirements (typically 3 kWh or more for residential storage). The 30% Investment Tax Credit applies whether the battery is installed alongside new solar or added to an existing system. Consult a tax professional regarding your specific situation, as the ITC reduces tax liability rather than providing a direct refund.
The Right Time to Add Battery Backup to Your Home Is Before the Next Outage
A solar battery backup system for home is not a luxury for the few. In a utility territory defined by rising rates, wildfire-related shutoffs, and aging grid infrastructure, battery storage has become practical energy insurance for Central Valley families. The California SGIP rebate and federal tax credit together make 2025 one of the strongest windows for this investment the state has seen.
Pacific Solar installs battery backup systems across Fresno and the surrounding Central Valley, including the Tesla Powerwall, FranklinWH, and Enphase systems. If you want to understand what a system would cost for your home and whether you qualify for SGIP, contact Pacific Solar for a free consultation.