Hay said FPL, which made $1 billion in profits last year, spent 1.64 cents on operations and maintenance for every kilowat hour sold, versus the industry average of 2.28 cents. He also wrote that FPL’s operations allowed the company to provide the “lowest electricity bill in Florida” for customers. A 2010 review of Florida’s large for-profit utilities found FPL customers on average waited 77 minutes to see their power restored, which was the quickest of the five providers.

On Monday, FPL spokesman Gibbs said investments in technology let FPL reduce costs without impacting service. “We’re just more efficient,’’ he said.

But Isaac brought a new challenge to FPL’s operations. With only a side blow from a tropical storm, some FPL customers were frustrated to be left without power — or any information on when it would return.

“This is ridiculous. It was a nothing storm,’’ James Clavijo, a finance executive in Miami Beach, wrote in an email after The Miami Herald requested reports from readers without electricity. Jose Castillo also responded, saying his Little Havana apartment complex on SW 10th Street lost power sometime Sunday night and hadn’t been restored by late afternoon Monday.

“My wife called FPL [and] was told it had been reported. So far we are way past 12 hours with no power,’’ he wrote. “No emergency lights at all. And it’s almost like a ghost town.”

Gibbs, the FPL spokesman, said more than 4,000 utility workers have responded to Isaac in South Florida. He said the utility could not say when power would be restored for most of the customers who lost electricity. He also urged customers not to assume they were being ignored.

“A lot of people get misled by not seeing a truck in their neighborhood,’’ he said. “I can tell you there are a ton of people working behind the scenes to get power restored.”

WLRN-Miami Herald reporter Kenny Malone contributed to this report.