(Adds comments, share price in paragraph 2, details about nuclear-powered hydrogen plant in paragraphs 8-10)

Nov 6 (Reuters) - Constellation Energy on Monday posted a quarterly profit and raised its annual core profit forecast, boosting shares to an all-time high, after the utility benefited from lower operating expenses and extreme weather increased power demand.

Shares of Constellation Energy rose by nearly 7% to $125 after the earnings release.

Record summer temperatures during the quarter in the United States drove people to crank up their air conditioning, increasing 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.

The Baltimore, Maryland-based company provides nuclear, hydro, wind, and solar-generated electricity to more than 20 million homes and businesses.

Its nuclear units ran at near 100% capacity during this year's hottest months.

Last week, Constellation Energy, the operator of the largest nuclear fleet in the United States, 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.

In October, the U.S. Department of Energy awarded seven regional hydrogen hubs $7 billion in federal funding to push the commercial-scale deployment of clean hydrogen. Constellation's nuclear-powered clean hydrogen production facility at its LaSalle plant in Illinois is among the projects selected.

"Certainly, we think that the hub award is a good sign, but we need to see the right rules or the hub won't happen," CEO Joseph Dominguez told analysts during an earnings conference call.

Constellation, and other nuclear plant operators, are waiting for the U.S. Department of the Treasury's guidance on whether the use of nuclear power to produce hydrogen qualifies for the Inflation Reduction Act's Section 45V Clean Hydrogen Production Tax Credit.

"I would say I'm cautiously optimistic," Dominguez said.

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.

Its third-quarter total operating expenses fell to $5.13 billion, down 15.7% from a year earlier. (Reporting by Nicole Jao in New York and Roshia Sabu in Bengaluru; Editing by Shinjini Ganguli and Barbara Lewis)