It's yet another economic indicator - as if Florida's tepid economy needs one.

Customer growth at the state's largest utility, Florida Power & Light Co., has dropped 79 percent during the past year.

And an increasing percentage of existing FPL customers are using extremely low amounts of electricity - a sign that more homes are sitting empty across the state, executives say.

"There's no question that the economy in Florida is unusually difficult," Lew Hay III, chairman and chief executive officer of FPL parent company FPL Group Inc., said Thursday during a conference call to report second-quarter results.

"That has affected us, and it will continue to affect us until economic conditions improve," Hay said.

Juno Beach-based FPL Group Inc. (NYSE: FPL) said second-quarter profit fell 48 percent compared with a year ago.

Though slow customer growth and lower electricity usage hampered earnings, the company attributed most of the drop in profit to a decline in the value of utilities contracts that its alternative-energy subsidiary signed when energy prices were lower.

Now that prices are higher, accounting rules require FPL Energy to report the $157 million change in value of the hedges as an after-tax loss.

"FPL, as well as several utilities in the nation, including private companies, have done a poor job of navigating volatile energy prices," said Mike Bedley, a partner with Apex Power Co. in Davie.

FPL Group's earnings for the three months ended June 30 were $209 million, or 52 cents a share, compared with $405 million, or $1.01 a share, during the year-ago quarter.

Revenue was $3.59 billion, down from $3.93 billion a year ago.

Not including the losses associated with the utilities hedges and another $9 million in temporary impairments, FPL Group met analysts' targets.

Adjusted earnings were $375 million, or 93 cents a share, on par with estimates from analysts polled by Bloomberg.

Adjusted earnings during the second quarter of 2007 were $348 million, or 86 cents a share.

Shares of FPL remained flat Thursday, gaining 36 cents to close at $64.53.

The housing slowdown has been a drag on Florida Power & Light's customer growth, and the utility added just 21,000 new customers during the second quarter. That's down from 95,000 during the second quarter of 2007.

Meanwhile, the number of homes consuming very little electricity - 200 or less megawatt hours a month - has climbed from about 7.2 percent of residential accounts in mid-2004 to about 8.2 percent.

The average residential customer uses about 1,140 megawatt hours.

"It all has to do with the housing market," Bedley said. "How many people have second condos and things sitting empty?"

The utility has about 4.5 million customers, about 4 million of whom are residential.

While overall retail sales of energy were up 3.2 percent for FPL, the gain was driven by warm weather during the quarter.

Still, executives said that they were pleased with the performance of FPL Group's two subsidiaries.

Florida Power & Light, the regulated utility subsidiary, reported net income of $217 million, or 54 cents a share, during the quarter, up 3 percent from $211 million, or 53 cents a share, during the year-ago period.

Revenue was $2.87 billion during the quarter, down from $2.91 billion a year ago.

FPL Energy, the wholesale-energy subsidiary that sells wind, solar and nuclear power, reported net income dropped 99 percent to $3 million, or 1 cent a share, on the $157 million losses from the utilities contracts.

That's compared with $203 million, or 51 cents a share, during the second quarter of 2007.

Revenue at FPL Energy was $663 million, down from $983 million a year ago.

The company reaffirmed its adjusted-earnings guidance of $3.83 to $3.93 a share for 2008.

"Although the current economic environment remains challenging, we continue to believe the long-term economic outlook for Florida is favorable," FPL Group's Chief Financial Officer, Armando Pimentel Jr., said during the call.