U.S. Midwest braces for another heat wave next week

Fri Jul 20, 2012 1:13pm EDT

* MISO issues hot weather alert for Monday

* Energy usage in SPP highest for 2012 on Thursday

* Highs in Oklahoma City over 100 degrees for days

By Scott DiSavino

July 20 (Reuters) - The Midwest power grid operator on Friday issued a hot weather alert for Monday, telling the region's generators and transmission owners to prepare plants and power lines for another heat wave next week.

The alert also tells transmission owners not to conduct any unnecessary maintenance on their equipment during the heat wave, the Midwest Independent Transmission System Operator (MISO) said in a release.

High temperatures in Chicago, the biggest metropolitan area in the Midwest were expected to reach 94 degrees Fahrenheit (34 Celsius) on Sunday and Monday, and 90 on Tuesday, Wednesday and Thursday, before falling to near normal levels in the 80s on Friday, according to weather forecaster AccuWeather.com.

MISO, which operates the power grid in 11 U.S. Midwest states and the province of Manitoba in Canada, forecast electric demand next week would be high, reaching about 93,400 megawatts (MW) on Monday, 94,600 MW on Tuesday and 93,300 MW on Wednesday, but was not expected to break any usage records.

During a brutal heat wave this week when the mercury hit 99 degrees in Chicago, peak demand was close to but did not break the system's all-time record of 98,526 MW set in July 2011.

One megawatt powers about 1,000 homes.

The biggest utilities in the MISO include units of Duke Energy, Xcel Energy, Ameren Corp, Berkshire Hathaway's MidAmerican Energy, DTE Energy and CMS Energy.

SPP HITS 2012 RECORD

The Southwest Power Pool (SPP), which oversees the grid in all or parts of Nebraska, Kansas, Oklahoma, Texas, New Mexico, Missouri, Arkansas, Louisiana and Mississippi, said peak demand on Thursday was the highest so far this summer.

Temperatures in Oklahoma City, a major market in SPP, hit the triple digits on Wednesday and Thursday of this week and were expected to top 100 every day until next Thursday, July 26, according to AccuWeather.com. The normal high in Oklahoma City is 95 degrees at this time of year.

SPP said Thursday's peak reached over 52,800 MW, which was the highest this year but was still below the system's all-time usage record of 54,949 MW set in August 2011.

For a factbox on peak power records in major grids in the United States and Canada, see

The biggest utilities in SPP include units of American Electric Power, Xcel, Great Plains Energy and OGE Energy.