(CNN) - In terms of the total number of lost hours of electricity, Puerto Rico and the US Virgin Islands are in the midst of the largest blackout in US history, according to a report from an economic research company.
In all, Hurricane Maria has caused a loss of 1.25 billion hours of electricity supply for Americans, according to the analysis from the economic research firm Rhodium Group. That makes it the largest blackout in US history, well ahead of Hurricane Georges in 1998 and Superstorm Sandy in 2012, the group said.
That 1.25 billion number will continue to grow. More than a month after Hurricane Maria knocked out the electric grid on the islands, the vast majority of residents remain without electricity, and the restoration of that power is months away.
The Rhodium Group analysis largely relies on data on electricity loss provided to the Department of Energy, as well as news reports for storms prior to 2000, according to Trevor Houser, a partner at Rhodium who co-wrote the analysis with Peter Marsters.
Houser said the group analyzes the economic impacts of weather and climate events, and they decided to dig in more deeply on the impacts of Maria on the Puerto Rican economy.
"As we started looking at the scale of the blackout and try to put that in historical context, it became clear this was a record-breaking event and worthy of some attention and focus just from an electric standpoint," Houser said.
9 of top 10 are hurricane-related
Other major storms or incidents have knocked out power for more people, but those were for shorter periods of time.
For example, the 2003 blackouts in the Northeast US affected about 30 million people, but the power was restored within a few days. That incident caused the loss of 592 million customer-hours of electricity, according to Rhodium Group, making it the eighth-largest blackout in US history.
Puerto Rico has a smaller population -- about 3.4 million -- but the blackout has lasted for a much longer stretch of time. As of Thursday, just 26% of households had power restored, according to data from the Puerto Rico Electric Power Authority (PREPA).
PREPA, a state-owned utility, filed for bankruptcy in July, is $9 billion in debt and is struggling to recover from the hurricane outages. Not coincidentally, several of the top 10 blackouts in US history involve Puerto Rico, including Maria and Irma this year and Hurricane Georges in 1998.
Whitefish Energy, a two-year-old utility firm with ties to the Trump administration, was awarded a $300 million contract from PREPA last week to help restore the country's power grid. The huge contract to a small company has led to questions and criticism from Puerto Rican politicians.
The Virgin Islands, with a much smaller population, has similarly struggled to restore power since Hurricane Maria. As of October 22, just 14.9% of customers had power, according to the U.S. Virgin Islands Water and Power Authority. That includes about 71% without power on St. Thomas, 98.4% without power on St. Croix and 100% without power on St. John.
Aside from the 2003 blackout, all of the biggest blackouts in US history were due to hurricanes or major storms, including Hurricane Hugo in 1989, Hurricane Ike in 2008, and Hurricane Katrina in 2005.
This year's hurricane season has been particularly destructive. Hurricane Irma, the Category 5 storm that tore through the Caribbean before hitting Florida in early September, caused the loss of 753 million hours of electricity, making it the fourth-largest blackout in US history.
In general, most power outages are due to disruption in the power lines that deliver energy, rather than in energy generation, Houser said. Hurricanes, with their high sustained winds and wide geographic area, are particularly likely to knock out power for large numbers of people.