Factbox: About 4.3 million still without power in U.S. Southeast after Irma

Most of the remaining outages were in Florida Power & Light's service area in the southern and eastern parts of the state. FPL, the state's biggest power company, said about 1.9 million had no power on Wednesday, down from more than 3.6 million on Monday.

NextEra Energy Inc-owned FPL, which serves nearly 5 million homes and businesses, expects to restore essentially all of its customers in the eastern portion of Florida by the weekend and the harder-hit western portion of the state by Sept. 22. It will take longer to restore those with tornado damage or severe flooding, FPL said.

Outages at Duke Energy Corp, which serves the northern and central parts of Florida, fell to 923,000 by midday on Wednesday, down from a peak of about 1.2 million on Monday, according to the company's website.

Irma hit southwestern Florida on Sunday morning as a Category 4 storm, the second most severe on the five-step Saffir-Simpson scale. It had weakened to a tropical depression on Monday.

In Georgia, utilities reported that outages declined to about 556,000 on Wednesday, down from a peak of around 1.3 million on Monday.

Other big power utilities in Florida are units of Emera Inc and Southern Co, which also operates the biggest electric companies in Georgia and Alabama.

(Reporting by Scott DiSavino in New York; Editing by Meredith Mazzilli)