Does solar work during a power outage?

Why solar shuts off in an outage without a battery

Your solar system shuts down during an outage because of a safety feature called anti-islanding protection. Grid-tied inverters are certified to UL 1741, which requires them to stop producing power the moment the grid goes down. That keeps your system from feeding power into the neighborhood’s lines during an outage, where it could injure utility crews working on the fault.

A standard grid-tied inverter turns itself off when utility power is lost and can’t supply backup power on its own. When the grid drops, your inverter detects the loss of voltage and frequency reference, and it stops converting DC power from your panels into usable AC electricity. The panels themselves are still generating voltage, but without the inverter operating, that power has nowhere to go.

This isn’t a design flaw — it’s intentional. Line workers could be hurt if the lines they’re repairing were still energized from distributed solar systems feeding power back into lines they assume are dead. Anti-islanding protection ensures your system doesn’t become a hazard during repair work.

To use solar during an outage, you need a battery backup system that can create an isolated circuit. With a backup-capable battery, the system senses the outage, disconnects from the grid and creates its own isolated circuit. Your inverter sees a stable connection and keeps producing, and the battery soaks up that solar and runs the house.

How battery backup systems work during an outage

A backup battery turns your home into its own small microgrid. When the grid fails, the battery inverter cuts the connection and runs your home as an independent island. The process happens in three stages.

First, the battery inverter or transfer switch detects the loss of grid power. A backup-capable system switches into island mode on its own and powers your chosen circuits from stored energy. Your home is physically disconnected from the utility lines, preventing any backfeed.

Second, the battery immediately begins supplying power to your home from its stored charge. There’s typically no interruption for critical loads — the switchover happens in milliseconds.

Third, once the isolated microgrid is stable, your solar panels recognize the battery inverter as their new grid reference and resume generating power. During daylight hours, your panels can recharge the battery while simultaneously powering your home, extending your backup runtime significantly.

This is the only configuration that allows you to use solar power during an outage. Without a battery, your solar system remains offline until grid power is restored. If you’re considering backup power, find an installer near you who can assess your home and size a system for your actual needs.

What a battery backup system actually costs in 2026

A backup battery system typically costs $10,000 to $16,000 installed, depending on capacity, brand, and installation complexity. That range reflects a single battery unit with enough capacity to run essential loads for 12-24 hours.

The most common residential battery is around 13.5 kWh of usable capacity. A 13.5 kWh battery can keep essential loads running for roughly 12 to 24 hours, assuming you’re powering a refrigerator, lights, a few outlets, your internet router, and possibly a sump pump or well pump. If you want whole-home backup or need to run heating and cooling equipment, you’ll likely need two or more batteries, which pushes the installed cost to $20,000-$30,000 or higher.

One important policy change: the federal residential credit (Section 25D) ended for installations completed after December 31, 2025, so batteries bought now get no federal credit. However, many states and utilities still offer battery incentives. California’s SGIP program, for example, provides rebates for battery storage, with higher amounts for customers in high fire-risk areas or with medical baseline needs. Check current incentives in your state before purchasing — they can offset 10-30% of the total system cost.

If your solar system was installed without a battery, most can be retrofitted. You’ll need a compatible battery inverter or a hybrid inverter replacement, plus the battery unit itself and any necessary electrical panel upgrades. Retrofitting typically costs slightly more than installing battery and solar together from the start, but it’s a viable option if you already have panels and want backup capability. Learn more about how solar panels work with and without storage.

How long will a battery keep your power on?

Runtime depends on three factors: battery capacity, what you’re powering, and whether your solar panels can recharge the battery during the outage.

Expect roughly 8 to 24 hours of backup for essential circuits, with the actual time depending heavily on what’s plugged in and how you use it. A refrigerator draws 100-200 watts when running, LED lights use 10-20 watts each, and a Wi-Fi router pulls about 10 watts. If you’re conservative with usage, a 13.5 kWh battery can stretch through a full day and night.

High-draw appliances change the equation fast. An electric water heater pulls 3,000-4,500 watts. Central air conditioning draws 3,000-5,000 watts. An electric range uses 2,000-5,000 watts per burner. Running any of these during an outage will drain your battery in hours, not days.

In sunny weather, solar can refill the battery every day, so solar plus storage can keep going through a long outage. If your battery discharges overnight and your panels produce enough energy the next day to fully recharge it, you can ride out multi-day outages indefinitely — assuming the weather cooperates. Cloud cover, winter sun angles, and shorter daylight hours all reduce solar output and limit recharge capability.

Most installers design backup systems around “essential loads” — a subset of circuits in your home that you select ahead of time. This typically includes the refrigerator, a few lights and outlets, the garage door opener, your internet and security system, and maybe a sump pump. Whole-home backup is possible but requires significantly more battery capacity and often multiple units.

Can you add battery backup to an existing solar system?

Yes, and it’s one of the most common retrofits we see. If your solar system is already installed, you can add a battery later. The process and cost depend on what type of inverter you currently have.

If you have a string inverter (one central unit, typically mounted on the side of your house or in your garage), you have two options. First, you can add a separate battery inverter that connects to your existing system. This is often called an AC-coupled battery system. The battery inverter manages the battery and handles the transfer switch function during outages. Your existing solar inverter stays in place. Second, you can replace your string inverter with a hybrid inverter that handles both solar and battery in one unit. This is cleaner and often more efficient, but it means removing your current inverter.

If you have microinverters (one small inverter mounted under each panel), an AC-coupled battery system is usually the only option. Brands like Enphase and Tesla offer battery solutions designed to integrate with microinverter systems.

The electrical work required varies by installation. Some homes need a critical loads panel — a secondary subpanel that feeds only the circuits you want backed up during an outage. Others need a main panel upgrade if your existing panel doesn’t have space for the additional breakers. These costs are in addition to the battery and inverter hardware.

Retrofitting a battery to an existing system typically adds $1,000-$3,000 in labor and electrical costs compared to installing solar and battery together initially. But if you already have solar and want backup power, it’s absolutely doable. Work with an installer experienced in battery retrofits to assess your specific system. If you’re not sure where to start, find a verified installer in your area who can evaluate your setup and provide a quote.

Do all battery systems provide backup power?

No. This surprises a lot of homeowners, but not all solar batteries are designed to provide backup power during an outage. Some battery systems are designed only for energy arbitrage — storing cheap power and discharging it during expensive peak hours — and lack the transfer switch and islanding capability required to operate off-grid.

You need equipment specifically built to supply backup power. Look for systems explicitly marketed as “backup-ready” or “off-grid capable.” These include an automatic transfer switch that disconnects your home from the grid when an outage is detected, and inverter logic that can form a stable microgrid without a grid reference.

The most common residential backup battery systems in 2026 include Tesla Powerwall, Enphase IQ Battery, LG RESU, Generac PWRcell, and SolarEdge Energy Hub with LG or BYD batteries. All of these are backup-capable out of the box. However, installer configuration matters — your installer must enable backup mode and properly wire your critical loads panel or backup circuits. If backup wasn’t configured during installation, your system won’t work during an outage even if the hardware supports it.

Before purchasing a battery, confirm three things with your installer: (1) Does this model support backup operation? (2) Will you configure backup mode and test it after installation? (3) Which circuits in my home will have power during an outage? Don’t assume every battery system includes backup — clarify it upfront. For more detail on battery options, see our comparison of Tesla vs SolarEdge batteries.

Tesla owners: if your system shows a fault after an outage, see our guide to Tesla inverter error codes.

What happens when grid power comes back?

When utility power is restored, your battery system detects the return of stable grid voltage and frequency. Most systems wait 30 seconds to five minutes to confirm the grid is stable before reconnecting. This prevents the system from reconnecting during brief flickers or unstable voltage conditions that could damage your equipment.

Once the grid is confirmed stable, the transfer switch closes and your home reconnects to utility power. Your solar system resumes normal grid-tied operation, and your battery shifts back to its standard mode — charging from excess solar during the day and potentially discharging during peak rate hours if you’ve configured time-of-use optimization.

The transition is automatic. You don’t need to flip any switches or reset anything manually. The system monitors the grid continuously and handles the reconnection on its own.

Some systems offer configurable settings for reconnection timing and behavior. For example, you might set your system to remain off-grid for a longer period after power is restored, giving the utility time to stabilize before your home draws power again. Or you might configure the system to prioritize recharging the battery immediately after an outage before exporting to the grid. These settings vary by manufacturer and are typically managed through a monitoring app.

One common question: will my battery recharge from the grid after an outage? That depends on your system settings. Some homeowners configure their battery to recharge only from solar, ensuring they’re not pulling grid power during expensive peak hours. Others allow grid charging to quickly restore backup capacity after a long outage. You can usually adjust this setting in your system’s app or web portal.