Just after midnight on Sept. 11, Eugenio Pereira awoke to the sound of tropical-storm-force winds slamming his Gainesville, Florida, home. Hurricane Irma had arrived. At 1:45 a.m., the power flickered out, and he was in total darkness.

Unlike large swaths of Florida that were facing days if not weeks without electricity, Pereira knew he would have power when the sun rose. He had installed rooftop solar panels two weeks before the storm, along with an inverter that allows him to use power from the solar panels without being connected to the grid. The next morning, he plugged an extension cord into the inverter, flipped it on, and let his 7-kilowatt rooftop solar array do the rest. He was able to use his appliances and his Wi-Fi, so he could continue his work as a home-based IT consultant while the neighborhood waited for grid power to came back on.

"We didn't have sun at all the day after the hurricane, but even with clouds, it was enough," he said.

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Hurricane Irma cut the power to about 6.7 million customers across Florida, as well as hundreds of thousands in Georgia, South Carolina and North Carolina. Only about two-thirds of those in Florida had power back by Thursday, and Florida Power & Light said the outages could last weeks in some areas.

It's a scene that plays out every time a major hurricane hits. But this time, homeowners like Pereira, some businesses, and even cities were able to take advantage of the Sunshine State's solar power while the grid was down.

Most rooftop solar arrays are connected to the grid, so when the public power is off, the rooftop solar power can't be accessed—unless the customer has a stand-alone inverter, like Pereira does, or a battery storage system like the Tesla Powerwall.

Local solar contractors and companies have been using the hurricane-induced power outages this week to experiment with these technologies to run their homes and businesses off-grid. In Jacksonville—where the storm surge reached record levels—Pete Wilking, president of A1A Solar Contracting, said he's been using his home rooftop solar and battery storage system the entire time since the storm. About 95 percent of his customers are grid-tied because it's the cheapest option, but he said some have batteries that they are using at full capacity now that it's sunny.

"Events like Irma have made people aware of how dependent we are on electricity," Wilking said.

Cities have also been putting off-grid solar power systems to work. Coral Springs, just northwest of Fort Lauderdale, used solar-powered traffic lights while its grid power was down.

During the worst part of the storm—when 300,000 people had lost power in Broward County—Coral Springs placed 13 lights in major thoroughfares throughout the city. Two small batteries sit beneath a solar panel that powers the light, which is placed on the ground at an intersection, said Derek Fernandes, traffic officer for Coral Springs. The batteries are used at night so the lights stay on.

"We were able to cover the major arteries in the city that didn't have power," Fernandes said. "One has been running since Monday, and we haven't had to replace it."

Opportunity to Redesign the Grid for Resilience

Solar advocates say that now—as the state rebuilds thousands of miles of damaged power infrastructure—is the perfect time for Florida to rethink grid resilience and bringing in renewable energy.

Alissa Jean Schafer, solar communications and policy manager for the Southern Alliance for Clean Energy, had just returned to the Fort Lauderdale area after evacuating with her family to Atlanta and was already having conversations with people in her community about the potential for distributed solar.

"If we're going to be taking steps toward resiliency, and people are still living in South Florida, [we have to] look at how to create a more resilient grid between having distributed resources like rooftop solar as opposed to only have power coming from one source, like natural gas," she said.

Solar can also help run microgrids that are able to continue providing power to a local area when the main grid is damaged elsewhere. "Microgrids could potentially make it easier to bring small communities back on quicker," Schafer said.

"The more spread out, the more resilient you're able to be," she said. "Those issues really come to a head when we see something go wrong."

Solar Support Is Growing, Despite Politics

Florida, for all its solar potential, is still in the nascent stages of what could become a solar boom.

Utilities are beginning to expand their renewable energy footprint: Florida Power & Light has announced plans for eight new solar plants across the state, and last month, Duke Energy canceled a nuclear project and said it will instead spend $6 billion building solar farms, installing electric vehicle charging stations, and improving the electric grid.

There is also a grassroots movement growing: last year, voters passed an amendment that extends a tax break for residents who have installed solar or equipment for other renewable energy. They also rejected a utility-backed solar amendment that would have raised fees and kept out companies wanting to compete with utilities to sell solar.

In recent months, solar cooperatives, which allow a community to buy solar together and save money, have also become a popular way to access rooftop solar; there are now nine in the state.

South Miami recently approved an ordinance that would require solar installations on all new homes and requires solar installations for any renovations that expand a home by more than 75 percent or replace more than 75 percent of the existing roof. Last month, St. Petersburg city officials proposed a similar ordinance. Orlando's sustainability officials have also expressed interest in advancing solar initiatives in the coming months. The city set its own renewable energy standard in August and is working to eliminate solar permit fees for certain residential and commercial solar systems.

Energy Storage Is Critical

To stave off another power outage of this scale, some energy experts say storage is the most important consideration to address.

Companies like Ikea and Tesla have started offering cheaper battery options for home solar systems. But "there needs to be some temporary incentive for the next two to three years to reduce the cost of storage for consumer to install storage systems," said Vikram Aggarwal, CEO of EnergySage, a company that offers an online marketplace for people to buy and sell solar.

Grid modernization is also key. The majority of Florida's transmission lines are above ground, and more than 70 percent of the grid relies on natural gas. Microgrids are rare in the state, so far.

Political Hurdles to a Solar Future

There are many climate and energy policy hurdles to cross before a modern power grid that take advantage of Florida's abundant solar power becomes a reality.

Florida is one of 13 states that still do not have a voluntary or mandated renewable energy standard. Florida Gov. Rick Scott has repeatedly questioned climate science (after Irma struck, he said he was still unsure), and two years ago his administration banned the use of the terms "climate change," "sustainability" and "global warming" in official documents. Hurricane devastation in Texas and Florida has still done little to sway many public officials of the role climate change played in the storms.

Still, those working on the ground with recovery efforts are hopeful this could be a turning point.

"I think this will lead to rethinking solar and rethinking resilience," Urban Paradise Guild President Sam Van Leer said after returning home from a long day of volunteering in Miami. One of the nonprofit's first requests as it set up an emergency shelter in a Miami warehouse was for solar generators and solar panels to help power the city. On Wednesday night, seven solar generators were being transported by semi trucks from out of state.

"On a macro scale," he said, "this hurricane may have catalyzed enough people to pay attention that politicians might actually have to act."