Over the next 20 years, the United States will need 1300 to 1900 new power plants.
Blackouts will become common in 20 years unless at least 1300 power plants are built before then.
mnli hypothesis: Blackouts will become common in 20 years unless at least 1300 power plants are built before then. premise: Over the next 20 years, the United States will need 1300 to 1900 new power plants.