Hurricane Ernesto left hundreds of thousands of Puerto Ricans without power on Wednesday as its wind and rain pelted the island’s frail electrical system.

More than 650,000 customers had lost electricity as of noon, Luma Energy, the power utility, reported. That amounted to about 45 percent of the nearly 1.5 million customers the utility serves.

Juan Saca, Luma’s president and chief executive, had warned of likely power outages ahead of the storm. The utility said crews would be ready to make repairs once weather conditions improved and it was safe for them to work outside.

In 2017, Hurricane Maria knocked out electricity across all of Puerto Rico, exposing the vulnerabilities of the island’s antiquated and inefficient power grid. Some people did not get their electricity back for more than a year.

The grid has been plagued by aging equipment, lack of maintenance and past mismanagement and corruption. Luma, a private Canadian-American consortium, took over the transmission and distribution of power in 2021. The bankrupt public utility, the Puerto Rico Electric Power Authority, known as PREPA, remains in charge of power generation. Puerto Ricans pay about 40 percent more for electricity than the average U.S. customer, according to the U.S. Energy Information Administration.

Ernesto became a hurricane on Wednesday just north of Puerto Rico after strengthening in the Caribbean. The storm is expected to strengthen further as it approaches Bermuda by this weekend, according to forecasters.