May 7 (Reuters) - Vistra Corp VST.N swung to a loss in the first quarter on Wednesday, as the independent power producer was hurt by setbacks in its hedging activities and higher costs, sending its shares down nearly 6% in early trading.

The company said the quarterly deficit was driven primarily by unrealized mark-to-market losses on derivative positions as energy prices increased in the forward periods.

Continued higher-for-longer interest rates weighed on the utility as it made investing in the construction and maintenance of critical infrastructure such as electrical grids more expensive.

Vistra's interest costs rose nearly 88% to $319 million in the quarter, while total operating expenses increased about 39% to $693 million.

However, the company said the performance was boosted by "two additional months" of results from the newly acquired nuclear utility Energy Harbor.

Its adjusted core profit from ongoing operations rose to $1.24 billion compared to $810 million a year earlier, helped by higher prices and strong retail performance.

Adjusted core profit in the retail segment stood at $184 million compared with a loss of $28 million a year earlier.

The utility expects load growth to increase at an annual rate of nearly 4% through 2030 with data centers accounting for about 40% of new demand.

Vistra reaffirmed current-year adjusted core profit from continuing operations of $5.5 billion to $6.1 billion, compared with the analysts' estimate of $5.9 billion.

The Irving, Texas-based company posted a net loss of $268 million for the three months ended March 31, compared with a net income of $18 million a year ago.

(Reporting by Vallari Srivastava and Katha Kalia in Bengaluru; Editing by Vijay Kishore)

((Srivastava.Vallari@thomsonreuters.com;))