How to Pick a Solar Panel and Battery Backup System

We asked a lot of experts how long these systems can last in an outage, generally speaking. The short and conservative answer: less than 24 hours on a single battery. But claims vary so widely that the thorough answer to this question is less conclusive.

In 2022, according to US Energy Information Administration figures, the typical US home consumed 29.6 kilowatt-hours per day. Even the largest single solar battery we were able to find in 2025, a Generac PWRCell, has a capacity of 21.6 kWh. “I don’t have to tell you that this cannot run your whole house for a day,” said EnergySage’s Aggarwal. But “how long can I run my home” is really the wrong way to think about solar storage in the context of a blackout. For one thing, you can expect your solar panels to both deliver power to your home and recharge your battery during the day — in sunny weather — thus continuously regenerating your backup power source. That adds a form of resilience that fossil-fuel generators lack, because once their gas or propane runs out, they’re useless until you can get more fuel. And that may be impossible in an emergency.

More to the point, during an outage, how much energy you conserve is at least as important as how much energy you can store. In order to make your battery last as long as possible, you’ll need to cut way back on your usage. Having lived through Hurricane Andrew in Miami, in 1992, I turned the challenges of that experience—no power for days, rotting groceries—into a line of inquiry. I asked all of the installers and battery makers I spoke to the same question: Assuming I want to keep the fridge running (for food safety), keep a couple of devices charged (for communication and information), and keep some lights on (for nighttime safety), how long can I expect a battery to last without recharging?

Keyvan Vasefi, head of product, operations, and manufacturing at Goal Zero, said he and his wife had run multiple tests on their 3 kWh battery, and they typically were able to go for a day and a half with “fridge running, multiple phone recharges, and master bedroom and bathroom with lighting.” They also did tests with their solar panels hooked to the battery. Even bearing in mind that Vasefi has an interest in selling this tech, he does make a compelling case for it: “We try to pretend it’s the end of the world and see what happens, and we can effectively get an indefinite run time” on those limited circuits, he said. “Batteries back to a hundred percent every day at 6:00 p.m. And we feel really good about that.”

A 10 kWh battery can typically run a fridge, some lights, and several device chargers for two to three days, said Sven Amirian, vice president of Invaleon, a Massachusetts-based installer. That timeframe was echoed by Aric Saunders, senior vice president of battery-maker Electriq.

When you get a battery installed, your contractor may ask you to choose a limited “emergency subset” of your home’s circuits, which they’ll then route through a subpanel. During an outage, the battery will feed only these circuits. (As an example, my dad has a propane backup generator at his home in Virginia, and it’s hooked up to one of his three air-conditioning units, the fridge, the kitchen outlets, an on-demand water heater, and some lights. The house doesn’t have TV, laundry, and other conveniences until the grid comes back. But having a partially cooled home and cold drinks has meant the difference between comfort and misery during the frequent summer blackouts.)

You can also manually shut off individual breakers in your panel to limit the battery to feeding only those you consider critical. And all solar storage batteries come with apps that show you which circuits are being used, helping you find and eliminate power draws that you may have overlooked. “In real time, you can change your habits and maybe stretch out an extra day,” said Amirian. Note, though, that customer reviews of the apps are the same kind of mixed bag that we find for every smart-appliance app we test: Some people love them, while others are frustrated by glitchy performance and buggy updates.

Finally, battery makers are beginning to offer smart panels. Via an app, they let you toggle individual circuits on and off remotely and thus customize which circuits are in use at various times (say, disabling the bedroom lights and outlets during the day and turning them back on at night).But Amirian cautioned that installing a smart panel is not simple or cheap. “There’s a lot of customer education that has to happen, the pros and cons, costs and benefits, of ‘I want to be able to control every circuit’ versus ‘That’s going to be $10,000 of electrical work for a two-day blackout.’”

The bottom line is that even with limited solar recharging, you’ll be able to increase the time you can maintain power off-grid — but only if you demand less of your battery. This reality was neatly described by Jonnell Carol Minefee, co-founder of Solar Tyme USA, a Georgia-based solar installer that focuses on rural, minority, and impoverished communities: “I understand we’re Americans, we love our whatever-whatever, but we have to learn how to exist without all our luxuries some of the time.”