Electric Reliability Threatened in Summer 2021

By NERC Project Coordinator Beth Davis


Noteworthy high temperatures, record spreading wildfires, and unrelenting drought have combined to stress the grid with peak electricity demands weeks earlier than anticipated. NERC’s 2021 Summer Reliability Assessment (SRA) issued in May identified areas of concern regarding the reliability of the North American BPS for the upcoming summer season. The SRA forecasts peak electricity demand and supply changes highlighting unique regional challenges or expected conditions that might impact the BPS. The reliability assessment process is a coordinated reliability evaluation between the Reliability Assessment Subcommittee (RAS), the six Regional Entities (RE), and NERC staff. The assessment provides an evaluation of the resource and transmission system adequacy that is necessary to meet projected summer peak demands for the upcoming summer period from June through September 2021. 

Significant deficiencies have been identified for four regions this summer. Texas RE and the Electric Reliability Council of Texas (ERCOT) and most of WECC expect above-normal levels of demand due to wide-area heat event caused energy emergencies. MISO and NPCC-New England also expect increased demands. 

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Weather officials anticipated above normal temperatures this summer, but the heat dome arrived earlier than expectedEffective preseason maintenance and preparations are particularly important to BPS reliability in severe or prolonged periods of above-normal temperatures such as the record busting temperatures being experienced in the Southwest.

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As much as 75% of WECC is experiencing the most severe drought in the past 20 years. California reservoirs are 50% lower than normal. Lake Oroville, the state’s second largest reservoir, is expected to fall so low this summer that it hydroelectric power plant will be forced to shut down for the first time since it opened in 1967. While California does not yet anticipate rotating outages, they are urging customers to voluntarily reduce consumption. 

The first-ever water shortage along the Colorado River is threatening the Hoover Dam with Lake Mead 143 feet below “full,” a loss of 5.5 trillion gallons. A “bathtub ring” of white minerals as tall as the Statue of Liberty exists along the shoreline. Hoover Dam power generation is down 25 percent affecting California, Arizona and Nevada. 

Much of Texas is also experiencing a drought and below-normal rainfall. Generator outages are expected to increase during severe and prolonged drought conditions due to cooling water supply and temperature issues. ERCOT indicates multiple generators are in forced outage for repairs. Consumers in Texas are being asked to conserve energy by setting thermostats at 78 degrees or higher and  turning off or unplugging unused appliances including pool pumps. 

Above-normal fire risk in the Southwest and over the middle-third of the country are setting the stage for an active fire season. States have experienced successive dry years and, when combined with lightning strikes or careless campers emerging from pandemic isolation, large uncontrolled wildfires once relegated to California are occurring from New Mexico to Montana. 

Wildfire prevention planning in California and other areas include power shut-off programs in high fire-risk areas. When conditions warrant implementing these plans, power lines (including transmission-level lines) may be preemptively de-energized in high fire-risk areas to prevent wildfire ignitions. In January 2021, the Electric Reliability Organization (NERC) published the Wildfire Mitigation Reference Guide to promote preparedness within the North American electric power industry and share the experience and practices from utilities in the Western Interconnection. 


Western Interconnection: Overall capacity and demand projections for the area are at similar levels to those seen in 2020 when a wide-area heat event caused energy emergencies and managed firm load loss from August 14 through August 19, 2020. During the event, Western Interconnection Balancing Authorities (BA) issued 18 separate Energy Emergency Alerts (EEA). Enhancements to day-ahead markets and operational planning that were put in place and were effective in mitigating the impacts of the second, higher temperature heat wave that extended across the Western United States in September 2020 will need to be employed again to support BPS reliability in similar conditions. 

MISO: MISO manages energy, reliability, and operating reserve markets that consist of 36 local BA and 394 market participants, serving approximately 42 million customers. Based on probabilistic studies performed by MISO, the area has low amounts of EUE (18.6 MWh) for the summer season. Greatest risk occurs in the month of July, coinciding with the typical peak in annual demand. 

NPCC-New England: The New England BPS serves approximately 14.5 million customers over 68,000 square miles. Based on an NPCC probabilistic assessment with scenarios, the New England assessment area is expected to require limited use of their operating procedures designed to mitigate resource shortages during Summer 2021. Negligible amounts of LOLE, LOLH, and EUE were estimated over the summer period for all the scenarios modeled except the severe low-likelihood case. The two highest peak load levels for this severe case resulted in LOLE of 0.3 days, with an associated LOLH of 1.3 hours, and an associated EUE of 868 MWh. This scenario is based exclusively on the two highest load levels representing an average 10–15% increase in peak loads over the 50/50 forecast with a combined 7% probability of occurrence. Additional constraints include 10% reduction in NPCC resources and PJM reductions. 

Texas RE-ERCOT: ERCOT is a summer-peaking RE that covers approximately 200,000 square miles, connects over 46,500 miles of transmission lines, has over 710 generation units, and serves more than 25 million customers. Above-normal summer peak load and outage conditions could result in the need to employ operating mitigations (i.e., demand response, transfers, and short-term load interruption).  

WECC-CAMX: WECC’s 329 members, which include 38 BA, represent a wide spectrum of organizations with an interest in the BES. Serving an area of nearly 1.8 million square miles and more than 82 million people, it is geographically the largest and most diverse of the NERC RE. Anticipated resources, which include new capacity in development as well as imports, are expected to be sufficient to meet summer peak demand. However, supply shortfalls from unanticipated low variable generation output, limited imports, or thermal generation outages could lead to energy emergencies. Extreme demand, as seen in 2020, could also lead to emergencies. 

WECC-NWPP & RMRG: WECC Northwest Power Pool and Rocky Mountain Reserve Sharing Group is an assessment area in the WECC RE. The area includes Colorado, Idaho, Montana, Oregon, Utah, Washington, and Wyoming and parts of California, Nebraska, Nevada, and South Dakota. Localized short-term operational issues may occur due to wildfires. Due to the widely dispersed nature of the transmission system, outages due to wildfires are generally not widespread.  

WECC-SRSG: WECC Southwest Reserve Sharing Group is an assessment area in the WECC RE. It includes Arizona and New Mexico and part of California and Texas. Localized short-term operational issues may occur due to wildfires. Due to the widely dispersed nature of the transmission system, outages due to wildfires are generally not widespread. 

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