(Adds Southern outlook in paragraph 7, CFO quote in 8; updates shares)
* Southern, Exelon, NextEra top market forecast
* Exelon's industrial demand remains weak
* Southern sees Southeast economic strength
* Southern Q3 EPS forecast slightly lags mkt view
* Exelon, Southern shares rise; NextEra down
By Matt Daily and Krishna N Das
NEW YORK/BANGALORE, July 27 Three top U.S. power companies posted higher-than-expected quarterly earnings on Wednesday, but drew a mixed picture of the nation's economic outlook and demand for electricity.
Exelon Corp , which operates the largest U.S. fleet of nuclear power plants, raised its full-year profit forecast based on results in the first half, when it relied on strong residential and small-business demand to offset weak electricity usage from industrial customers.
NextEra Energy , the largest U.S. renewable energy producer, said its earnings benefited from greater demand at its Florida Power & Light utility and stronger output from its wind farms, but warned of uncertainty ahead.
"The economic recovery in Florida appears to continue to take hold, but the progress is slow and uneven," Chief Financial Officer Armando Pimentel Jr. told a conference call.
Still, Southern Co , which is trying to build the first U.S. nuclear power reactor in decades, said demand had increased in its markets.
"The industrial sector continues to lead the economic recovery in the Southeast," Chief Executive Thomas Fanning said in a release. "Our region is well-positioned for future expansion, and we are already seeing new business development in several parts of our service territory."
The Atlanta-based company forecast third-quarter earnings of $1.02 a share and backed its full-year profit outlook of $2.48- $2.56 a share. Analysts were predicting a third-quarter profit of $1.07 a share, according to Thomson Reuters I/B/E/S.
"This industrial recovery is very broad-based, with all major segments except for the housing-related segments of stone, clay, and glass and textiles experiencing year-over-year growth," Chief Financial Officer Art Beattie said on a conference call with analysts.
Southern's second-quarter profit increased 18 percent to $603.3 million, while revenue rose 7 percent to $4.52 billion.
Exelon's quarterly profit rose 39 percent to $620 million. The company, which is seeking regulatory approvals to buy Constellation Energy Group , raised its full-year forecast to between $4.05 and $4.25 per share from a prior range of $3.90 to $4.20.
Exelon forecast no growth in 2011 overall power demand from customers of its PECO utility in Pennsylvania and Commonwealth Edison customers in Illinois, largely because of moribund demand from its largest users.
NextEra's profit jumped 39 percent to $580 million, even though extended refueling outages at its Seabrook and Point Beach nuclear power plants cut into its earnings. Its shares fell 1.09 percent.
Shares of Exelon were up 1 percent while those of Southern recouped losses to turn positive. (Writing by Matt Daily; Editing by Lisa Von Ahn and Gunna Dickson)