Hurricane Ian’s catastrophic winds and flooding are likely to bring long-lasting power outages to large parts of Florida. The storm is the latest in a line of hurricanes and extreme heat and cold events that have knocked out power to millions of Americans in recent years for days at a time. In many disaster- and outage-prone areas, people are starting to ask whether investing in rooftop solar and battery storage systems can keep the lights on and the air conditioner running when the power grid can’t. When the grid goes down, most solar systems that lack a battery will also shut down. But with batteries, a home can disconnect from the grid. Each day, the sun powers the home and charges up the batteries, which provide power through the night.
How Much Can Solar + Storage Do? For a new report, we modeled a generic power outage for every county in the U.S., testing whether a rooftop solar system combined with a 10- or 30-kilowatt-hour battery could power critical loads, like refrigeration, lighting, internet service and well pumps; if it could go further and also power heating and air conditioning; or if it could even power a whole home. To put that into perspective, the most popular battery on the market, the Tesla Solar Powerwall, has just over 13 kWh of storage.
How Solar Would Have Handled 10 Past Disasters We also looked at 10 real-world outage events from 2017 to 2020, including hurricanes, wildfires and storms, and modeled building performance for specific locations and real weather patterns during and after the outages. We found that in seven of the outages, most homes would have been able to maintain critical loads plus heating and cooling using solar with 30 kWh of storage, or just over two Powerwalls.
New Forms of Backup
Setting up solar and storage to provide backup power in a home or building takes extra work and it costs more – just one Powerwall can run from $12,000 to $16,500 for a full system installation, before incentives and taxes. That’s as much as a fair-sized solar system. Nevertheless, a growing number of homeowners are installing both. Over 90% of new solar installations in Hawaii in 2021 were paired with batteries after a regulation change. Now these distributed power plants are helping power the grid as coal plants are retired. California has over 1.5 million rooftop solar systems. A growing number of customers are retrofitting batteries on their systems, or adding new solar plus storage, in part because utilities have resorted to “public safety power shutoffs” to lower the risk of wildfires sparked by power lines during dry, windy days. And new forms of backup power are emerging, especially from electric cars. Ford is partnering with SunRun to combine its new F150 Lightning electric pickup truck with solar and a two-way charger that can use the truck’s battery to power a house. The standard version of the truck comes with a 98-kWh battery, the equivalent of more than seven Tesla Powerwall stationary batteries.
Critical Power for Critical Services A fire station in Puerto Rico offers a glimpse of what solar and storage can do. After Hurricane Maria cut power for months in 2017, over 40,000 solar systems were installed on the island, often paired with battery storage. One of those is at the fire station in the town of Guánica, which had been unable to receive emergency calls in previous outages. When Hurricane Fiona’s wind and flooding again knocked out power to most of Puerto Rico in September 2022, the fire station was still operating.
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