Hurricane Sally cuts off power to more than 540,000; power demand sinks 16%

Houston — More than 540,000 electricity customers lost service across Alabama, Florida, Georgia and Mississippi after Hurricane Sally made landfall early Sept. 16, sapping power demand by 16.4% from forecast or more than 20% from the same time Sept. 9, and bilateral traders bid down power prices accordingly.

With wind speeds topping 105 mph, Sally was categorized as a Category 2 storm as it made landfall about 4:45 am ET near Gulf Shores, Alabama, according to the National Hurricane Center. As of about 5 pm ET, more than 543,000 customers were without power at utilities monitored by PowerOutage.us across the four affected states.

Southern Company's Alabama Power was hardest hit in terms of number of customers, closely followed by Gulf Power, which is now part of NextEra Energy but remains part of Southern Company's balancing authority, a system of ensuring reliability by instantaneously matching power loads with supplies.

As of about 1 pm ET Sept. 16, the Southern Company balancing authority had 23.5 GW of power demand, but it had forecast a load of 28.1 GW, according to the US Energy Information Administration, a difference of 16.4%. At the same time a week earlier, Sept. 9, load was 29.5 GW, so the week-on-week difference was 20.1%.

Day-ahead on-peak power to be delivered Into GTC traded down about $1.50 to about $19/MWh, and the Into Southern Company index traded down about $2 to about $18/MWh, according to S&P Global Platts assessments.

PowerSouth Energy Cooperative, a generation and transmission electric cooperative with members in Alabama and Florida, was also hit hard.

'Historic and catastrophic flooding'

For example, virtually all of the Baldwin Electric Membership Corp.'s 78,037 customers were without power around 2:30 pm Sept. 16.

"Our crews will begin assessment and restoration efforts as soon as it is safe to do so," Baldwin said on its website the afternoon of Sept. 16. "We are receiving multiple reports of power lines down and broken poles across our service area. Due to the widespread damage, we do expect extended outages."

Sally had weakened to a tropical storm by the time the National Hurricane Center's 2 pm ET update was released, but the 5 pm ET release indicated maximum sustained wind speeds remained around 60 mph with higher gusts, and Sally was forecast to become a tropical depression by the morning of Sept. 17.

Sally produced rain totals of 10 to 20 inches with isolated areas receiving 30-35 inches from Mobile Bay, Alabama, to the Florida Panhandle west of Tallahassee, the NHC said.

"Historic and catastrophic flooding, including widespread moderate to major river flooding, will continue across this region," the NHC said in its 5 pm ET update.