By Richard Branson and Amory B. Lovins

More than a month after Hurricane Maria devastated Puerto Rico, nearly 80 percent of the island remains without power, and food and water can be tough to find. As we rally to help the survivors and look to rebuild, we owe it to the victims there and in hurricane-ravaged Texas, Florida and elsewhere in the Caribbean to build more resilient infrastructure and prevent and reduce such destruction.

Rebuilding the electric grid in Puerto Rico will take months. But blackouts requiring weeks or months to fix are not caused by hurricanes alone. Many of the affected areas are powered by obsolete grids using fossil fuels. These fragile systems are easily knocked out by storms. We can’t eliminate hurricanes. But if we modernize the electric grid, we can stop blackouts caused by monster storms while also saving fossil fuel and reducing emissions of the greenhouse gases that warm the planet and make these storms more likely and destructive.

When one of us (Richard Branson) emerged from his cellar after riding out Hurricane Irma’s assault on Necker Island, the house and everything surrounding it was destroyed — except for the solar power array, which laid flat on ground and remained materially intact. Solar power systems survived Irma and kept working in Florida and Haiti. While Hurricane Harvey cut some Texas power lines, no wind farms were destroyed.

But that does not mean people with their own solar panels or other renewable energy systems managed to keep on their electricity. Though most of those systems were operable immediately after and often even during the storm, they couldn’t produce a watt of power. Outdated utility rules disabled them, not high winds.

After Superstorm Sandy hit New Jersey in 2012, more than 90 percent of the solar panels survived, but utility rules required that solar systems tied to the grid be shut down to guard against voltage surges that could endanger repairmen fixing the power lines. Homes that should never have lost power, or should have recovered it immediately, waited weeks for grid repairs they didn’t need. But modern power electronics have resolved the utilities’ legitimate safety concerns.

Inverters can be installed that can separate solar systems from the main grid, automatically or manually, and allow the solar systems to continue operating even though the grid is down. Unfortunately, nearly all utilities forbid this. In fact, Florida Power and Light lobbied the Legislature hard this year to restrict their customers from access to home-based solar systems when the grid goes down.

We should use this opportunity in Puerto Rico and other places hit hard by recent storms to do two things: Rebuild damaged or destroyed homes and businesses to be as energy efficient as possible, and rebuild the grid so that alternative energy systems like solar and wind, whether on a home or in a microgrid, can operate independently when the larger grid is damaged or shut down. (Microgrids are small networks of electricity users who rely on a local generating source like solar that is usually attached to the larger grid but can operate independently.)

The need for affordable, clean, reliable, resilient power is most acute for the majority of people of Caribbean island nations who pay high prices for electricity generated by burning imported oil and often paid for by imported capital. A nation like the Bahamas can spend a substantial part of its tourist industry’s earnings just to run its electricity system, and other islands are even worse off.

Our organization, the Rocky Mountain Institute, works with the Clinton Foundation, international and regional partners, governments and utilities to help Caribbean island nations switch to modern and regionally abundant solar and wind power. Those efforts were going well before the latest hurricanes. Solar arrays in the Turks and Caicos Islands and on Cooper Island in the British Virgin Islands, among others, survived the hurricanes without damage and were able to provide electricity to nearby communities.

With those storms behind us, we must work to rebuild stronger, fuel-free, stormproof power systems based on decentralized and resilient renewables like solar. We need to use 21st century innovation, not 20th century technology. Importing fossil fuels costs these island nations enormous sums. Yet the sun shines and the wind blows on these islands for free. We’re optimistic we can do this. But we’ll have to resist our own impulses to carry on with business as usual.

We can learn from the experience of another Caribbean nation — Cuba. Most electricity in the country was restored within a week after Irma struck in early September; in Havana, took just three days. More than a decade ago, Cuba modernized its Soviet-era power plants and centralized grid. In 2005 serious blackouts occurred on 224 days. In 2007 the island’s move to decentralized energy cut that to zero. Now, when hurricanes like Irma hit, many parts of Cuba can sustain vital services.

What was Cuba’s resilient formula? First, the efficient use of power, which helped renewables do more at lower cost. Millions of efficient light bulbs, fans, rice cookers, pressure cookers, refrigerators, air-conditioners and pumps were sold nationwide, reducing power usage.

Most important, Cuba added over 1,800 decentralized diesel and fuel-oil-fired electrical plants across the island and upgraded the infrastructure of the grid itself. Cuba lets these local plants or microgrids disconnect from the island’s grid during storms or blackouts and generate their own electricity for local needs. This allows these microgrids to serve their own customers, then reconnect to the larger grid later.

Microgrids are becoming proven and popular around the world from India (where record floods couldn’t stop solar power) to the University of California at San Diego, whose microgrid (powering 92 percent of the campus and saving $8 million a year) reversed flow and sent power back to the utility in less than a half-hour (until wildfires ate a power line).

Some traditional utilities oppose microgrids as a threat to their beleaguered monopoly. But giant electrical equipment firms like Siemens, Schneider and General Electric now offer microgrids, and nearly 2,000 projects were underway worldwide at the end of 2016.

Simple, sensible improvements like these can make our families, communities and nations more secure and durable; save money and create important new value in the electricity, fuel and real-estate industries.

When storms, earthquakes, wildfires or cyberattacks take down our brittle power grid, we should all be able to start rebuilding our homes and lives immediately, with our smartphones and water pumps, filling stations and traffic lights, computers and refrigerators, continuously powered by the world’s greatest uninterruptible power supply — the sun.

Richard Branson is the founder of the Virgin Group. Amory B. Lovins is a co-founder of the Rocky Mountain Institute, where he is chief scientist.

See this OP-ED article at www.NYTimes.com