SAN JUAN, P.R. — Like many other frivolous things on the island these days, the shiny motorcycles at the Planet Honda showroom have been pushed to the side.

In their place are dozens of folding chairs, and on Thursday morning, they were all filled with Puerto Ricans waiting to buy the most essential machines on the post-hurricane landscape: portable generators, to light their powerless homes.

María Aguilera, 57, a teacher, was waiting in the line that had formed outside the showroom Thursday morning. When the sun sets these days, she said, she relies on candles for light. And like everyone else in Puerto Rico — including Gov. Ricardo A. Rosselló — Ms. Aguilera said she had no idea when the power grid might be restored.

“From the things I’ve seen with the infrastructure,” she said, “it could be months.”

Hurricane Maria’s near total destruction of the commonwealth’s electric power grid has transformed Puerto Rico into Generator Island. Running on gas or diesel, and ranging from lawn mower to moving-truck size, the generators are the only option for the roughly 90 percent of the island that has no access to the decimated grid. Generators now power big-box stores, high-rise apartment buildings, auto shops, fast-food restaurants, wastewater treatment plants and little country homes. And their low, incessant groan is the new drone note in the discordant symphony of post-storm Puerto Rican life.

The generators are a temporary fix that is raising health and safety concerns and highlighting the stark divisions of class in a place with a 45 percent poverty rate. They are also the only option for most Puerto Ricans for now, as the island struggles with restoring its electrical system — by far the most important and complex challenge the storm has presented.

In a news conference on Friday, Mr. Rosselló could not say when the system, which was infamously fragile before the storm, would be fully restored.

“There is no estimated date right now,” he said. “We have established, right at the beginning of this week, we want to have 10 percent of the energy generation in Puerto Rico. Now we’re up to 10.6 percent. And our expectation is, within the next month, to have 25 percent.”

Many big-box stores and hardware stores are selling out of generators for home use. Julito Ramírez, the Planet Honda general manager, said that his company was having a hard time keeping up with demand, selling 250 to 300 units per day. After ordering all of the generators he could find in the United States, he has turned to a cache he found in Canada.