May 1 (Reuters) - U.S. utility Pinnacle West Capital PNW.N on Thursday swung to a loss in the first quarter, hurt by higher operating and interest costs.

The Phoenix, Arizona-based company's operating and maintenance costs rose due to new power plants and intangible assets.

Higher-for-longer interest rates also hurt utilities, which typically need higher capital to construct and maintain infrastructure such as grids.

The company said its total operating expenses rose to $975.1 million during the first quarter, from $884.9 million during the same reporting period a year ago.

Its total interest costs rose to $94.8 million during the quarter, from $86.6 million a year ago.

Shares of the company were down marginally in morning trade.

The utility, however, said the number of retail customers grew 2.3% in Arizona, where electricity demand is accelerating, partly driven by multibillion-dollar semiconductor plants coming online.

Pinnacle West's main subsidiary, which serves 1.4 million customers primarily in Arizona, expects to add 9,805 megawatts (MW) of renewable power, battery storage and natural gas between 2025 and 2028, with over 90% projected to be carbon-free, the company said in February.

It posted a net loss of $4.6 million, or 4 cents per share, for the quarter ended March 31, compared with a year-ago profit of $16.9 million, or 15 cents per share.

(Reporting by Arunima Kumar and Khusbu Jena in Bengaluru; Editing by Sahal Muhammed)

((Khusbu.Jena@thomsonreuters.com;))