By Scott DiSavino
July 5 (Reuters) - Real-time power prices in the Midwest Independent Transmission System Operator (MISO) in the U.S. Midwest were over $1,000 per megawatt-hour for at least an hour Thursday afternoon during a brutal heat wave, the grid operator said on its website.
On-peak power prices in the MISO usually average about $60 per MWh at this time of year.
But with temperatures expected to reach the triple digits in several of the largest metropolitan areas in the grid, and with some unexpected power plant outages, the MISO put out a maximum generation emergency warning on Thursday.
The warning, issued at about 2 p.m. Eastern time, called on generators outside the MISO territory who had previously agreed to sell power into the MISO market to schedule those resources.
The biggest power grids surrounding the MISO include PJM to the East, Ontario to the North, the Southwest Power Pool (SPP) to the West and Southwest, and TVA to the Southeast.
Demand for power in the MISO was expected to reach about 94,700 megawatts (MW) on Thursday and 91,500 MW on Friday, still well below the grid’s all-time record of 98,526 MW set during a brutal heat wave on July 20, 2011, according to the MISO.
Temperatures in Chicago, the biggest metropolitan area in the Midwest, were expected to reach the triple digits for a second day in row with a high of 102 degrees Fahrenheit (39 Celsius) forecast for Thursday and 100 for Friday before dropping to the low 80s by Sunday, according to AccuWeather.com.
The normal high for this time of year in Chicago is about 84 degrees.
Power traders could not say which power plants may have shut but did note that generation from wind resources went from about 3,000 MW late on July 4 to just 700 MW by midday on Thursday.
By about 3:30 p.m. Eastern time, the problem seemed to be over as real-time prices in the MISO dropped to more-normal levels in the $30s per MWh.
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.