AGUADILLA, PUERTO RICO (NYTIMES) - Four years after Hurricane Maria left Puerto Rico's electrical grid a shambles and the entire island in the dark, residents had expected their fragile power system to be stronger now. Instead, unreliable electricity remains frustratingly common, hindering economic development and daily life.

In June, a private consortium known as LUMA Energy took over the transmission and distribution of electricity. And yet the situation has only worsened. Surging demand in August and September led to rolling blackouts affecting a majority of the island's 1.5 million electrical customers.

Last week, several thousand people marched along a main highway in San Juan, the capital, blocking traffic with the latest in a series of protests over the seemingly unending electricity problems plaguing the island.

"The people can't take it anymore," said Iris Delia Matos Rivera, 69, a former employee of the island's longstanding electrical utility who attended a recent demonstration.

Many Puerto Ricans are diabetic and need refrigerated insulin to survive. The coronavirus pandemic has also put some people on respiratory therapies requiring electrical power at home for oxygen machines. Some Puerto Ricans are still studying or working at home.

Ashlee Vega, who lives in northwestern Puerto Rico, said the power fluctuations this month were so imperceptible that it took her several hours to realise her appliances were not working right. The new refrigerator she had bought in February - to replace an old one that gave out after enduring years of volatile electrical surges - was fried.

Her mother lent her a big cooler. In went the milk and eggs, the ham and cheese. Vegetables spoiled. Twice a day for the next five days, until a repairman got her fridge working, she hustled to gas stations for ice. There was little to be had at first because a spate of power outages had also left her neighbours scrambling.

"I can't have that happen again," said Vega, 31, an Army veteran who returned last year to Aguadilla, her hometown, from Colorado with her 7-year-old son, Sebastián. "That's not something that should be happening. We're in 2021. We have internet on our TV. Why don't we have electricity?"

Behind the failures are the same problems that have plagued Puerto Rico's grid for decades: ageing equipment, lack of maintenance and past mismanagement and corruption of an inefficient system.

The bankrupt public utility, which is still in charge of power generation, declared an emergency this month to try to hasten critical repairs to its ailing plants. Electricity rates, which are higher in Puerto Rico than in almost all of the 50 states, have continued to rise, even as service has deteriorated.

Privatising transmission and distribution - the part of the power system most damaged by Hurricane Maria - has led to new challenges, including public distrust and the retirement or redeployment of experienced line workers who knew how to deal with the island's outdated infrastructure.

The system is so frail that a power plant recently went offline because sargassum - seaweed - blocked its filters.

The inability of the Puerto Rico Electric Power Authority, known as PREPA, and the new private Canadian-American consortium to provide consistent power has led to weeks of finger-pointing, tense legislative hearings and growing protests by fed-up residents who ousted the governor two years ago by taking to the streets.

"That LUMA contract has to be thrown in the trash!" protesters chanted Friday.

Crews patched Puerto Rico's grid with US$3.2 billion (S$4.3 billion) in emergency repairs after Maria, which shredded the island's power lines as a Category 4 storm in September 2017. Congress earmarked about US$10 billion through the Federal Emergency Management Agency to rebuild the system. Those projects will be contracted out by the new consortium, with the aim of restoring the grid to how it was before the storm, with some modernisation.

That approach, while consistent with how the federal government deals with disasters, is shortsighted and unsustainable, said Agustín A. Irizarry, an electrical engineering professor at the University of Puerto Rico who has promoted a plan to distribute solar energy across residential and commercial rooftop panels and storage batteries.

"People are doing it on their own, without the government stepping in," he said. "Eventually, there won't be clients for the electrical grid because they will not have taken the trouble to modernise the grid."

Last week, the government of Puerto Rico announced the first disbursement of federal funds for reconstruction: US$7.1 million.

Puerto Rico awarded a 15-year contract to LUMA last year to operate the transmission and distribution system and handle its reconstruction, arguing that a private company would do better than PREPA, one of the two largest public power utilities in the United States. While PREPA is in bankruptcy - it is US$9 billion in debt - Puerto Rico is paying the new company a fixed annual fee of US$115 million.

Gov. Pedro R. Pierluisi said the new contract came with a promise to reduce the number and length of outages. But the contract drew criticism from the start, with some analysts noting that the company would not face penalties if it did not find savings and lower rates.

LUMA took over in June, with its top officials saying they were prepared to handle a Category 2 hurricane. (None have hit the island this year.) Almost immediately, huge outages began.

Customers found the company slow to respond to their complaints. Some residents tried to fix the grid themselves, prompting the utility to warn against such dangerous attempts.

Wayne Stensby, LUMA's chief executive, said in an interview in June that the company had rolled out a new website and app to provide better customer service, opened call centres on the island and planned a series of other improvements, including upgrading the vehicle fleet.

He blamed the initial rash of problems on a backlog of outages, a cyberattack and resistance from some PREPA workers ahead of the June 1 hand-off, including a blockade to keep LUMA from accessing some equipment.

Some power lines, he added, were still being held up by the makeshift fixes made after the hurricane, in which crews restored electricity by tying the lines not to poles but to trees.

Stensby said in a congressional hearing this month that fixing the tattered system would take time. The company has cleared half the backlog of solar power applications - some of them two years old, he said - and has a batch of 65 initial projects worth about US$2.8 billion that it hopes to begin next year.

"The Puerto Rico electric system is arguably the worst in the United States and has been for a very long time, even prior to the devastating hurricanes in 2017," Stensby said. "While the transformation is in its early days, we have many reasons to be optimistic."

But records filed by LUMA from June through August show outages lasted longer on average than they did last year under PREPA: more than five hours, compared with less than half that time in the same months of 2020. (The US average is about 82 minutes.) Stensby said in the congressional hearing that the system remained precarious - and that customers under-reported their outages previously because they did not expect the utility to be responsive.

Puerto Rican legislators have demanded to know exactly how many line workers LUMA has employed. PREPA historically had about 800. Stensby said at the hearing this month that the company had about 900, but he did not specify how many had prior experience in Puerto Rico, other than saying a large portion of them did.

Legislators have also asked how many executives are making salaries greater than US$200,000 a year. The company has refused to respond, despite being ordered by the Puerto Rico Supreme Court to do so.

Juan Declet-Barreto, a senior social scientist for climate vulnerability at the Union of Concerned Scientists, is part of a coalition that has urged the Biden administration to withhold federal funds used to pay the company unless safeguards are added to the contract and it better aligns with the White House's policy goals of promoting renewable energy and protecting workers' rights.

Otherwise, the funds will be wasted, Declet-Barreto said. "And when another hurricane comes, it won't have to be a Category 5 - with a tropical storm, half of the island will be left without power," he said.