Meanwhile, Tampa Electric, a unit of Emera Inc., said Saturday that because of Irma's shift westward the storm could cause up to 500,000 of its customers to lose power, or up to 70% of its system.
The number of homes and businesses without power in Florida as Hurricane Irma pummels the southern part of the state approached 600,000 Sunday morning.
"We will safely shut down these nuclear plants well in advance of hurricane-force winds, and we've finalized plans for that shutdown", FPL spokesman Rob Gould told a news conference.
The company, which serves about 10 million power customers across almost half of Florida, may have to physically rebuild parts of the power system, Gould said. Even as Houston flooded, the power stayed on for most, allowing citizens to use TV and radio to stay apprised of danger, or social media to call for help. If the hurricane continues on its present track and strength, Florida's west coast could be more of a "rebuild" to restore power, he said. It could become a Category 5 at any time.More news: Apple iPhone shortfalls seen as result of early manufacturing glitches
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FPL says it has invested $3 billion to protect its electricity grid since 2005, when the last major hurricane damaged power facilities in Florida.
FPL's two nuclear plants, Turkey Point and St. Lucie, will be closed on a gradual scale in advance of the onset of winds.
48 hours after landfall, county by county estimates are given and finally 96 hours after landfall they provide restoration estimate at a more local level.