More resilient, small-scale electric systems powered by the sun are looking increasingly attractive for Caribbean islands plunged into darkness after hurricanes Irma and Maria, .

In making the case for so-called microgrids, environmental nonprofit Rocky Mountain Institute pointed to solar installations on the Turks and Caicos islands that remained largely intact while the local utility reported more than 1,200 poles down. That was the case on Richard Branson’s Necker Island, too.

Bruce Walker, the nominee to lead the US Energy Department’s electricity

office, said Puerto Rico’s devastated grid as an opportunity to test technologies that will make it more reslient to storms.

The catch is the price tag. By Rocky Mountain Institute’s estimates, it would cost roughly $250 million to build about 90 megawatts of solar and storage across a chain of Caribbean islands. That’s enough to power an estimated 15,000 U.S. homes. While it may be sufficient for the Turks and Caicos, about a million households live in storm-battered and debt-ridden Puerto Rico.

Bloomberg News energy analyst said Yayoi Sekine, “But without state support or external funding, it’s very difficult to actually see community microgrids flourish or have any investment at all.”

Sunnova Energy Corp., Puerto Rico’s largest rooftop solar-power supplier, has no idea whether its 10,000 systems survived back-to-back hurricanes this month. And even if they did, the panels wouldn’t be able to power customers’ homes, John Berger, the company’s chief executive officer, said in an interview Thursday.

That’s because rooftop panels rely on the local power system to deliver electricity, even if the power is just going to the customer’s house. And with Puerto Rico’s energy infrastructure out of commission, possibly for months, Sunnova’s panels aren’t able to help.

“It was devastating,” Berger said. “The distribution system was destroyed.”

That’s where batteries come in. Microgrid advocates say small systems that run on solar panels backed up by energy storage could help prevent widespread blackouts by steering dependence away from the antiquated, centralized systems islands now depend on.

The Islands Energy Program is working with 10 otherwise diesel-hungry Caribbean islands to develop energy plans, analyze the economics and identify the stakeholders to make projects market-ready. Someone still has to finance the initiatives, but since the hurricanes there’s been interest in adding to relief efforts, Locke said.

Statia Utility Co., the electricity and water provider for the Caribbean island of St. Eustatius, already generates about 23 percent of its power from a solar park primarily funded by the Dutch Ministry of Economic Affairs. The grid-tied installation had been hardened for Category 4 hurricane-strength winds, so it was unscathed by Irma and Maria, said Fred Cuvalay, the utility’s chief executive officer.