In response, more than 50,000 workers from the US and Canada have assembled at staging areas across the affected states, EEI wrote.
Florida's Division of Emergency Management reported Tuesday morning that 5 million customers didn't have electricity.
Major utilities in the state - including Florida Power & Light Co, Duke Energy Corp and Tampa Electric - have mobilized tens of thousands of workers to deal with the enormous power outages, which by Monday evening numbered more than 7.4 million homes and businesses after Hurricane Irma landed as a Category 4 storm early Sunday. Something they have been saying since "day one" was how Hurricane Irma was going to be different than Hurricane Matthew because Volusia wouldn't be one of the few counties affected.
As of Monday morning, more than 6.1 million utility customers were without power in Florida, Georgia and SC, it reported.
That's what Gus Beyersdorf, 40, and his colleague Nick Jensen, 32, utility workers from Wisconsin, found out while inspecting power lines in Florida on Monday.
They say the restoration process has been 4 times faster than what we saw during Hurricane Wilma 12 years ago. Once the damage and flooding caused by Irma is assessed starting Monday morning, cellphone service should resume for most customers soon after.
An army of 50,000 restoration workers from across the USA and Canada are working on the state's power grid, according to an Edison Electric Institute estimate. "We've had minimal impact on our generation facilities". Then we go to the feeder lines.
Dinneen said residents have to be patient, because the power companies are also working to get power in other areas in Florida that were more impacted by Irma.
"Hurricane Irma didn't leave the state until early Monday, and then we had to wait until winds were under 35 miles per hour", Mauldin said. At the same time, they're working to restore power to supermarkets and pharmacies.
On Monday morning, as Gov. Rick Scott departed for an aerial tour of the Keys Monday to view the extent of the physical damage, he urged patience.
It may be weeks before some get their power back, because electrical systems in some areas may need rebuilding, FPL has warned.
"If you are not sure, walk away from it, because you could have a power line that is still energized", he said.
As part of its 17,000-worker restoration effort that FPL said was the largest ever, FPL trucks were seen rolling throughout the region, including in Homestead, which had gone completely dark.
That's according to FPL's recovery plan.
While FPL hopes to have power back to all customers on the eastern seaboard by the end of the weekend, customers on the west side could be without power until September 22. About 90 percent is still without electricity as officials prioritize Homestead Hospital and the police and fire stations.