U.S. Midwest in danger of rotating power blackouts this summer

© Reuters. FILE PHOTO: An electrical line technician works on restoring power after a tornado Vilonia, Arkansas April 29, 2014. REUTERS/Carlo Allegri

(Reuters) - The power grid in the Central United States could be forced to impose rotating blackouts this summer as rising demand and plant retirements may result in capacity shortfalls on the hottest days, federal energy officials said in a note on Friday.

The Midcontinent Independent System Operator (MISO) has said "capacity shortfalls in both the north and central regions of MISO ... (leave) those areas at increased risk of temporary, controlled outages to preserve the integrity of the bulk electric system."

MISO operates the power grid for some 42 million people in 15 U.S. Central states from Minnesota to Louisiana and the Canadian province of Manitoba.

The U.S. Energy Information Administration (EIA) said on Friday that forecast demand in MISO could reach an hourly peak of 118.2 gigawatts (GW) under normal conditions this summer and 125.2 GW in extreme conditions.

To meet that peak demand, MISO expects to have 143.2 GW of capacity available this summer. One gigawatt can power about a million U.S. homes on average, but as little as 200,000 on a hot summer day.

But planned maintenance and forced outages could reduce that capacity, EIA warned.

In the past five years, MISO's summer capacity has been reduced by an average of 6.7 GW of maintenance outages, 14.4 GW of forced outages and 9.6 GW of seasonal derates like drought, low-wind conditions and fuel supply limitations.

All of those reductions could leave MISO with just 114.9 GW of generating capacity, which is less than its summer demand forecasts.

MISO said it and member utilities have trained for worst case scenarios this summer and are prepared to take actions to maintain grid reliability.

Those actions include urging homes and businesses to conserve energy, limiting power plant and transmission line maintenance during heatwaves and, if necessary, imposing rotating blackouts.