MISO warns rolling blackouts may be needed as demand strains grid

MISO warned on July 21 that rolling blackouts may be needed if demand keeps outrunning available generation across its 15-state Midwest and central U.S. footprint. The first outages would likely hit households, businesses and industrial customers after reserve plants, imported power and other emergency tools were exhausted.

The system must maintain resource adequacy, meaning enough available power to meet peak demand at all times. Summer heat can drive air-conditioning use sharply higher, and a June heat wave lifted electricity demand across the eastern and midwestern United States. In that kind of stress, grid operators may be forced to call on reserve units or neighboring grids, then move to controlled outages to keep the larger system from failing.

MISO’s 2026/2027 LOLE study put its summer planning reserve margin at 7.9%, compared with 11.6% in fall, 18.9% in winter and 23.4% in spring. The annual risk profile has shifted partly from summer toward winter, driven mainly by higher load forecasts and a significant volume of new solar resources.

Aging power plants, maintenance outages, fuel constraints and extreme weather can all narrow the margin for error. Rising demand from data centers, manufacturing expansion and electrification of transport and heating is increasing pressure just as wind and solar output continue to vary by weather and time of day.

The strain is not limited to MISO. PJM Interconnection ordered emergency steps and emergency electricity conservation during a heat wave on July 3 and July 6 to avoid large-scale outages, and MISO issued an energy emergency alert for the central U.S. on July 15.

MISO calls the issue a “Reliability Imperative,” and its 2026 Reliability Imperative Report is set up as a living document updated as conditions evolve. Its 2025 OMS-MISO Resource Adequacy Survey Results help utilities, regulators and state officials evaluate emerging risks and align planning efforts.