Recasts, includes executive quotes and new details throughout

May 6 (Reuters) - Constellation Energy CEG.O has been hit by rising costs to build and operate its electricity infrastructure, with the major U.S. power company on Tuesday missing Wall Street expectations for first-quarter profit.

Higher-for-longer interest rates can heap costs on utilities, making investing in the construction and maintenance of electrical grid infrastructure more expensive.

The company's net income fell around 87% from a year earlier to $118 million in the reported quarter.

Constellation Energy said interest expenses rose nearly 15% from a year earlier to $146 million in the January-March quarter, while total operating expenses rose 18.5% to $6.34 billion. Inflation, more broadly, is driving up costs, company executives said.

"It's clear that we're in a whole new ball game on cost," Constellation CEO Joseph Dominguez said on a company earnings call. Certain natural gas plant builds, for example, have tripled in cost over the last decade in some cases, Dominguez said.

Constellation Energy expects a 1-2% U.S. tariff impact on capex plan, including fuel, for 2025 and 2026, the company said.

Still, Constellation was moving ahead with power deals with data centers, including with the reopening of the former Three Mile Island nuclear reactor and on its $16.4 billion acquisition of privately held natural gas and geothermal company, Calpine.

Constellation shares rebounded in early trade, rising about 6%, after falling nearly 5% in premarket trading.

While the Calpine deal has faced backlash from consumer groups in the Mid-Atlantic area, Constellation executives said the company was on track to be completed by the end of the year.

It defended its planned acquisition of Calpine to the regulators last month.

The Baltimore, Maryland-based utility, posted an adjusted profit of $2.14 per share for the three months ended March 31, missing analysts' estimates of $2.22, according to data compiled by LSEG.

(Reporting by Katha Kalia and Sumit Saha in Bengaluru, Laila Kearney in New York; Editing by Krishna Chandra Eluri)

((Laila.kearney@thomsonreuters.com))