Feb 19 (Reuters) - Southern Co SO.N forecast annual profit below analysts' estimates on Thursday, and raised its five-year spending plan as it prepares to support unprecedented power needs from large-load customers such as data centers and industrials.

U.S. utilities have been investing heavily to upgrade electric grids as they face an onslaught of extreme weather and ballooning demand from power-hungry data centers dedicated to AI and cryptocurrency, alongside a shift by homes and businesses toward electric heating and transport.

Southern Co expects to spend about $81 billion from 2026 through 2030, compared with its prior five-year plan of $76 billion.

The utility said it had contracted 10 gigawatts of large load customers across Alabama, Georgia and Mississippi, including Google GOOGL.O, Meta META.O, Microsoft MSFT.O and Compass Datacenters. Its shares rose more than 2% in premarket trading.

With 9 million customers, Southern Co ranks as the second-largest U.S. utility, serving the states of Alabama, Georgia, Illinois, Mississippi, Tennessee and Virginia.

For the quarter ended December 31, Southern Co posted an adjusted profit of 55 cents per share, below analysts' expectations of 57 cents, according to data compiled by LSEG.

Its operating expenses jumped 14.7% during the quarter, while revenue rose 10%.

The Atlanta, Georgia-based company expects adjusted profit for 2026 to be between $4.50 and $4.60 per share, with the midpoint slightly below the estimate of $4.56 per share.

(Reporting by Vallari Srivastava in Bengaluru; Editing by Shilpi Majumdar)

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