How long do solar batteries last?

Determining how long a solar battery will last is a bit like asking how far a tank of gas—or an EV battery charge—will get you: It depends on where you're going and how you're driving. If you're just keeping your fridge cold and your WiFi running during a power outage, you might be able to stretch a single charge for a day or two. But fire up your air conditioning, and that same battery could be drained in a few hours.

The good news? Most homeowners find that a properly sized battery keeps their essential appliances running long enough to ride out typical outages. And if you pair that battery with solar panels, you're no longer limited to one charge. As long as the sun is shining, you can continue to recharge your battery and power your home—even if the grid remains down for days or weeks.

We'll walk you through what determines how long your battery will last on a single charge, explain how solar energy changes the equation entirely, and cover what to expect over your battery's 10-to 15-year lifespan.

The short answer: It depends on what you're trying to power and how big your battery is. But for most homes with a standard battery, you're looking at roughly a day of backup for your essential loads.

To understand why, it helps to know that the average American home uses about 30 kilowatt-hours (kWh) of electricity per day. That's everything—your heating and cooling, major appliances, electronics, lights, the works. Most home batteries store between 10 and 20 kWh, which might sound like it falls short. That’s why it’s important to only keep the essentials running during an outage—unless you have a whole-home backup battery, of course. 

Answering the following three questions will help you determine exactly how long your battery will power your home:

How big is your battery?

Battery capacity indicates the amount of electricity your battery can store at once, measured in kilowatt-hours. Think of it like a fuel tank: A larger tank holds more fuel, which means you can drive farther before needing to refill.

Most home batteries today fall somewhere between 10 and 20 kWh of storage capacity. A 13 kWh battery is pretty common—that's what you get with the popular Tesla Powerwall 3. Some systems let you stack multiple batteries together if you need more capacity, which is worth considering if you have high electricity needs or want to power more of your home during outages.

Battery capacity isn't the only spec that matters, though. There's also its power rating, measured in kilowatts (kW), which determines how much electricity your battery can deliver at once. A battery might have plenty of storage capacity but a lower power rating that limits how many appliances you can run simultaneously. Most modern batteries provide between 5 and 15 kW of continuous power. The Tesla Powerwall 3 offers 11.5 kW—enough to run most household circuits at the same time.

How much electricity are you using?

Different appliances pull wildly different amounts of power. What you choose to run during an outage makes a huge difference in how long your battery lasts.

Your refrigerator might use around 200 watts when it's running. LED light bulbs use about 10 watts each. Your WiFi router pulls another 10 watts or so. A TV might use 100 watts. Phone chargers? Maybe 20 watts for fast charging. Keep all of these running—call it 250-300 watts total for your must-have essentials—and a 13 kWh battery could theoretically power them for more than 40 hours.

But let's say you want to run your central air conditioning on a hot day. That AC unit might pull 3,000 watts or more. Suddenly, your battery runtime drops to just a few hours. Or maybe you're using a space heater in winter, which can draw 1,500 watts. Add that to your other essentials, and you're looking at significantly shorter backup time.

The more appliances you run, and the more power-hungry they are, the faster your stored capacity disappears. This is why most homeowners choose which circuits they want to back up ahead of time. You might decide to keep your fridge, a few lights, your internet, and some outlets powered—but skip backing up your central AC, electric water heater, or clothes dryer. It's about making strategic choices that balance comfort with runtime.

For a typical household with essentials running—fridge, lights, WiFi, phone charging, TV, and possibly a laptop or two—a 13 kWh battery will provide about a day of backup power. If you're more conservative with what you run, you might stretch that to 30 or even 40 hours. Use more power-hungry appliances, and you could drain it in half that time.

Do you have solar?

Everything we've talked about so far assumes you're working with a single charge—whatever electricity your battery had stored when the power went out. Drain it, and you're done until the grid comes back online.

Pair that battery with solar panels, though, and the entire calculation changes. Now, you're no longer limited to one charge. During daylight hours, your solar panels generate fresh electricity that, depending on the battery you choose, can simultaneously power your home and recharge your battery. When the sun sets, you switch to battery power. When the sun rises again, your panels kick back in and top off your battery for another night.

This cycle can continue almost indefinitely—with maybe a few recharge breaks—as long as the sun keeps coming up. Even if you have a couple of cloudy days where your solar production drops, once the weather clears, you're back to generating enough electricity to keep your battery charged and your home running. 

Without solar, you're watching the clock and rationing every kilowatt-hour. With solar, you're managing daily cycles instead of counting down to zero.

It's the difference between having a day or two of backup power and having backup that lasts as long as you need it—days, weeks, even months if necessary. That's why pairing solar with storage has become a popular choice for homeowners seeking genuine energy independence, especially in areas where extended power outages are a real concern.

When people ask how long batteries last, they usually mean one of two things: How long do they run on a single charge, or how many years before they need replacement? We've covered the first question—now let's talk about the second.

Most solar batteries maintain strong performance for 10 to 15 years before needing to be replaced. That's not to say your battery stops working at year 10. But batteries gradually lose capacity over time, and eventually they degrade to the point where replacement makes more sense than continuing to use them.

Battery degradation works similarly to what happens with your phone or laptop. Every time you charge and discharge the battery—known as a cycle—it loses a tiny bit of capacity. This is unavoidable, although some battery chemistries handle it better than others. Modern lithium-ion batteries, particularly lithium iron phosphate (LFP) batteries, have proven to be pretty resilient. They can handle thousands of charge-discharge cycles before their capacity drops significantly.

Most manufacturers guarantee their batteries will retain at least 60-70% of their original capacity after 10 years. So if you bought a 13 kWh battery, after a decade of use, it might only store about 9 kWh. That's still useful—it'll power your essentials for about 17 hours instead of 24—but it's a noticeable drop in performance. At some point, usually around that 60-70% capacity threshold, most homeowners decide it's time for an upgrade.

Battery warranties reveal a lot about the expected lifespan. A 10-year warranty is fairly standard these days, although some premium manufacturers offer 12, 15, or even 20 years of coverage. These warranties typically promise your battery will maintain a minimum percentage of its original capacity throughout the warranty period.

Just watch out for the fine print. Many warranties include a cycles clause or throughput limit. This means your warranty might end early if you use your battery more heavily than expected. For example, if your warranty covers 6,000 cycles over 10 years, and you cycle your battery twice a day instead of once, you could hit that limit in about 8 years instead of the full 10. Some manufacturers have started offering unlimited cycle warranties to alleviate this uncertainty—worth considering when comparing options.

Whether you're wondering how long backup batteries will last during an outage or how many years your battery will last, getting the most from your investment comes down to smart planning upfront and good habits over time.

Start by being realistic about what you actually need during an outage. Then, size your system accordingly. When comparing quotes for battery systems, dig into the warranty details. And work with an experienced installer who understands how to optimize your system for both performance and longevity—proper installation makes a real difference in how well your battery performs over its lifetime.

The right battery system won't just keep your lights on during the next storm. It'll give you confidence knowing you can handle whatever the grid throws at you, whether that's a quick afternoon outage or a multi-day power failure. And when you pair it with solar, you're not just buying backup power—you're investing in the kind of energy independence that keeps your home comfortable and connected no matter what's happening with your utility company.