US Grid Operators Warn Rolling Blackouts as Heat Wave Strains Power Supply

Midcontinent Independent System Operator (MISO) warned on July 21 that rolling blackouts could become necessary across its 15‑state Midwest and central U.S. footprint if peak demand outpaces available generation. The summer reserve margin sits at 7.9%, far lower than the 18.9% winter level, and a recent June heat wave pushed electricity use sharply higher. MISO said the first outages would likely affect households, businesses and industrial customers after emergency tools and imported power are exhausted.

At the same time, the Southwest Power Pool (SPP) issued a Level 3 Resource Advisory covering portions of 14 central states, indicating that reserve generating capacity is largely depleted. While no controlled outages have yet been ordered, officials warned that conditions remain fragile and could prompt rolling blackouts if demand continues to climb or additional plants fail. The advisory lists states such as Arkansas, Iowa, Kansas, Louisiana, Minnesota, Missouri, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas and Wyoming. Both operators highlighted the growing strain on the electric grid from extreme weather, rising consumption, and a variable renewable energy mix.