Emergency backup solar power systems: What to know before the next outage

Power outages are getting longer and more common. The average American household experienced about 11 hours of outage time in 2024, according to the U.S. Energy Information Administration (EIA)—and that number keeps growing.

If you've lost power during a heat wave, a winter storm, or a hurricane, you already know what's at stake: spoiled food, no AC or heat, medical devices losing power, and the general frustration that you're at the mercy of your utility company. Not only that, but power outages can cost up to $25,000 if property damage is involved.

An emergency backup solar power system has become a much more practical and affordable solution over the past few years. Rather than relying on a gas-powered generator that needs fuel, or simply hoping the power comes back quickly, you can pair solar panels with a home battery to store energy and keep your home running business as usual through outages. 

It's not magic, and it's not cheap, but for the right homeowner, it can be worth every penny.

An emergency backup solar power system combines rooftop solar panels with a home battery (often called a solar battery or energy storage system). The panels generate electricity from sunlight during the day, and the battery stores excess electricity that you don't immediately use. When the grid goes down, your home draws from that stored energy instead.

Some systems are designed for whole-home backup, meaning they can keep nearly everything in your house running during outages. Others are set up for "essential loads" backup, which means they power only your most critical circuits (i.e., refrigerator, lights, Wi-Fi router, medical equipment). The right setup depends on your energy needs and budget.

If you already have solar panels, you can add a battery or multiple batteries to your system. This is called a battery retrofit, and it's an increasingly popular option for homeowners who want emergency backup power or want to save more on their electric bills.

On a normal sunny day, your solar panels produce electricity, your home uses what it needs, and any extra either charges your battery or flows back to the grid. During an outage, your system automatically disconnects from the grid (a required safety feature to prevent utility workers from being electrocuted by power from your home) and switches to island mode. At that point, your battery becomes your power source.

During daylight hours, your solar panels will continue to generate power and recharge your battery, which means a well-designed backup solar power system can run for days as long as the sun is shining. At night or during extended cloudy weather, you're using the energy stored in the battery until it's depleted.

One thing to know: Not all solar panel systems automatically provide backup power during an outage. Standard grid-tied solar systems without a battery will shut down when the grid goes out, even if the sun is shining. The battery is what makes emergency backup possible.

Generators have been the default backup power option for decades, and they're not going anywhere anytime soon, but there’s a reason many homeowners are ditching their gas generators for solar and battery systems. Kris, the founder of City Prepping—a home preparedness community—told EnergySage that he believes having solar and batteries is a far better solution for long-term emergency backup.

“Once you run out of whatever fuel source a generator needs—diesel, propane, natural gas—you're done. It's pretty much a paper weight at that point, unless you can get access to fuel,” said Kris. “As long as you learn how to manage and ration your power usage, solar and a battery is going to be easily your best option.”

A gas or propane generator is cheaper upfront—typically $500 to $5,000 for a portable unit or $7,000 to $15,000 for a whole-home standby model. But the catch is the ongoing fuel cost, the need to store fuel safely, and the maintenance that comes with any internal combustion engine. Generators also produce carbon monoxide, which means they must be operated outdoors, and they're loud.

A solar battery system has higher upfront costs but no fuel expenses, no emissions, and minimal maintenance. It has a set-it-and-forget-it design that kicks on automatically when you need it. The biggest downside is that a single battery can only store about enough to power your essentials for a couple of days. But paired with solar panels, it could power your home indefinitely, so long as there's sun.

For many homeowners, the choice between solar batteries vs. generators depends on how long and how often outages tend to happen in their area. Short, infrequent outages? A battery-only system or small generator might suffice. Long, recurring outages due to severe weather or grid instability? A solar-plus-storage system is likely your best option.

While the federal residential solar Investment Tax Credit (ITC) for solar-plus-battery systems expired in 2025, many state and local incentives are still on the table. Many states offer their own tax credits, rebates, and net metering programs for solar, battery, and combination systems that can reduce what you pay or increase your electricity savings. Some utilities offer additional battery-specific rebates, so it’s worth researching what's available in your area or asking a reputable solar contractor to find incentives for you.

How long your home battery lasts depends on how much energy you have stored and what appliances you’re running. A single 10–13.5 kWh battery running only essential loads (fridge, lights, Wi-Fi) can last one to two days without any solar recharging. With solar panels replenishing the battery during daylight hours, that system can theoretically run indefinitely, as long as the sun is shining.

Here's a rough example: Say you have a 13.5 kWh battery that's fully charged when an outage starts. You're running your refrigerator (about 150 watts), some LED lights (50 watts total), and a Wi-Fi router (10 watts). That's around 210 watts of continuous draw, or about 5 kWh per day. Your battery alone would last about two and a half days. Add a solar panel system generating even 5–10 kWh per day (a partially cloudy estimate), and you could extend that significantly or indefinitely.

If you want to run something more energy-hungry, like central air conditioning or a washer/dryer during an outage, you’d need two to three batteries minimum, and ideally enough solar panels  to offset that additional load.

Some battery systems, like the Enphase IQ Battery 5P and the Tesla Powerwall 3, offer real-time monitoring apps so you can track your stored energy and manage usage during an outage.

For some homeowners, a backup solar-plus-storage system is worth every penny. For others, a simpler and cheaper solution makes more sense. A few factors that tend to push the math toward "yes":

The best first step is to get quotes from local solar installers who have experience designing backup systems. Not all solar companies specialize in storage, so ask directly whether they've completed solar-plus-battery projects in your area.

When you compare quotes, you’ll want to look at a few key features:

• Battery capacity (kWh)

• Which loads are included in the backup panel

• The inverter type (some hybrid inverters support both solar and battery)

• The warranty for both the panels and the battery.

On the EnergySage Marketplace, you can register for free and receive multiple quotes from pre-vetted installers. If you let them know you're interested in battery backup, they'll include storage options in their proposals so you can compare apples to apples. Our Energy Advisors can also help you sort through the tradeoffs and make sure you're not paying more than you should.