Matthew did not come on shore and damage infrastructure, and it took the utility about two days to restore power.
In all, nearly 1.8 million FPL homes and businesses had lost power.
More than 60,000 workers from across the United States and Canada were involved in the restoration efforts, including those from the affected companies and other utilities, said Tom Kuhn, president of the Edison Electric Institute, an industry trade group.
In the Tampa Bay area, almost 550,000 Duke Energy customers and more than 280,000 TECO customers remain without power. A unit of NextEra Energy Inc and the state's biggest power company, FPL said its outages held at around 3.6 million for much of Monday morning.
The total number of customers still out, representing about 9 million people in Florida, Georgia and the Carolinas, dipped from a peak of more than 7.8 million customers, or over 16 million people, on Monday. Emera's Tampa Electric utility said the storm could affect up to 500,000 of the 730,000 homes and businesses it serves.
Erdogan dismisses North Atlantic Treaty Organisation concerns overs Russian Federation defence system deal
He was referencing the US decision to arm the Kurdish YPG for the fight against ISIS in Syria, despite fierce protest by Turkey . The S-400 is Russia's next-generation, most advanced long-range anti-aircraft missile system.
Irma hit southwest Florida on Sunday morning as a unsafe Category 4 storm, the second-highest level on the five-step Saffir-Simpson scale.
The crews will help with power restoration efforts. It had weakened to a tropical depression on Monday.
Florida outages for Duke Energy Corp, which serves the northern and central parts of the state, held at around 1.2 million, according to the company's website, and Duke's outages in North and SC eased below a peak of 160,000. FPL reduced power at one reactor at the St. Lucie nuclear plant due to salt buildup in a switchyard from Irma.
Appalachian Power has 1 million customers in Virginia, West Virginia and Tennessee.