Nov 6 (Reuters) - Constellation Energy on Monday posted a quarterly profit and raised its annual core profit forecast, as the utility benefits from lower operating expenses and higher electricity demand due to extreme weather.

Summer temperatures during the quarter set new records in the United States, pushing people to crank up their air conditioning, and boosting electricity demand.

"Our generation fleet performed at peak levels during a summer of record heat, while our commercial business continued to win new business and realize higher margins," Chief Financial Officer Dan Eggers said in a statement.

Last week, Constellation Energy completed a $1.75 billion purchase of NRG Energy's 44% stake in the South Texas Project Electric Generating Station, a 2,645 megawatt nuclear facility.

Baltimore, Maryland-based Constellation raised its 2023 adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) outlook to a range of $3.8 billion to $4.0 billion from $3.3 billion to $3.7 billion previously.

It said its third-quarter net income attributable to shareholders stood at $731 million, or $2.26 per share, in the three months ended Sept.30, compared with a loss of $188 million, or 57 cents per share, a year earlier.

Quarterly profit also beat the average analyst estimate of a profit of $1.42 per share, according to LSEG data. The company generates electricity through its nuclear, hydro, wind, and solar generation facilities and powers more than 20 million homes and businesses.

Its third-quarter total operating expenses were down 15.7% to $5.13 billion from a year earlier.

(Reporting by Roshia Sabu in Bengaluru; Editing by Shinjini Ganguli)