Most outages were still in FPL's service area in the southern and eastern parts of Florida.
"This is likely to be one of the largest and most complex power restoration efforts in US history", said Tom Kuhn, president of the Edison Electric Institute, an industry trade group.
"The industry's Irma response is one of the largest power restoration efforts in USA history", Kuhn said.
In Georgia, utilities reported nearly 390,000 customers without power. That was down from a peak over 1.4 million on Monday night.
They have now been moved to Miami at the request of Florida Power and Light.
At least 17 storm-related deaths have been reported in the states. As ports began to reopen, queues of tanker trucks waited to be refilled.
It was too soon to say what the power restoration would cost FPL, but in 2016, the company said it spent about $315 million to restore power after Hurricanes Hermine and Matthew, according to NextEra's federal filings.
Irma, categorized as one of the most powerful Atlantic storms on record when it rampaged through the Caribbean, has killed at least 77 people, including 36 in the United States, officials said.
FPL has warned customers to prepare for outages that could last weeks if Irma requires the utility to rebuild parts of its service territory.
While most Californians were still sleeping, more than 100 Pacific Gas & Electric utility workers began deploying to help restore power in Florida.
Floridians who weathered the historic storm must now cope with an unprecedented loss of power: About 15 million people were without electricity across the state, the Department of Homeland Security said Tuesday.
St Lucie is located on a barrier island on the state'seast coast, about 120 miles north of Miami, while Turkey Point is about 30 miles south of Miami.