Many electric customers lost service as Hurricane Hermine made landfall in Florida and moved over portions of several southern states in early September. Electricity use in the city of Tallahassee, Florida, dropped rapidly in the hours after the hurricane's landfall around midnight on September 2, falling to less than 20% of forecast normal hourly demand. Service was not back to near normal levels until at least three days later.

The city of Tallahassee, which operates its own electric system as a balancing authority, reports its hourly actual and forecast demand to EIA. The largest difference between forecast demand and actual load occurred on September 2 between 8:00 a.m. and 9:00 a.m., when electricity load was 51,000 kilowatthours while forecast demand was 296,000 kilowatthours, an 83% difference. More than 80% of Tallahassee's customers experienced electricity service interruptions, based on local government sources.

Tallahassee's electricity use recovered from the outages within the week. On September 2, daily electricity load was 72% below the demand forecast, and by September 7, the load was just 1% below the demand forecast. Other neighboring balancing authorities, such as Jacksonville and Gainesville, also experienced some outages during the hurricane, although the impact was less severe.

Hurricane Hermine was classified as a tropical cyclone from August 31 through September 3, reaching a peak wind speed intensity of 80 mph. Hermine was the first hurricane to make landfall in Florida since Hurricane Wilma in 2005, and the first to develop in the Gulf of Mexico since Hurricane Ingrid in 2013.

Source: National Oceanic and Atmospheric Administration, National Hurricane Center, National Oceanic and Atmospheric Administration, National Hurricane Center, Advisory #014

EIA recently began collecting and publishing hourly electricity operating data, including actual and forecast demand, net generation, and electricity interchange between electric systems. The survey includes data from all 66 electric system balancing authorities that make up the contiguous U.S. electric grid.

Principal contributor: Cara Marcy