By Tim Fryfogle, Principal Engineer – Resources, Engineering & System Performance

ReliabilityFirst annually conducts seasonal reliability assessments, analyzing resource adequacy in our region using data provided by PJM and MISO. The Summer Reliability Assessment is published each year at the onset of the period of warmer weather experienced across the summer months in the RF region.

The upcoming summer season is projected to bring with it a normal risk to reliability in the PJM and MISO footprints under a more typical electric demand forecast, according to ReliabilityFirst (RF) analysis.

Using data provided by both PJM and MISO, we conduct our annual summer reliability assessment using two forecast scenarios:

1. The 50/50 demand forecast, which projects a 50% likelihood that electricity demand exceeds projected load. This demand scenario is considered more likely to occur but less likely to result in outages.
2. The 90/10 demand forecast, which projects a 10% likelihood that electricity demand exceeds extreme load. This high demand scenario is considered less likely to occur but more likely to result in outages.

These scenarios are used to evaluate whether available resources can meet demand under both typical and stressed system conditions. The analysis helps to determine overall reliability risk in PJM and MISO for the upcoming summer season.

PJM

When assessing PJM’s 50/50 demand forecast, PJM is projected to have adequate resources to serve normal electric demand in the upcoming summer season, including during expected periods in which certain generation resources become unavailable. PJM’s planning reserve margin requirement is 18.6% for the 2026 planning year, and its forecasted reserve margin is above that requirement at 26.2%.

Using historical resource (i.e., generation) performance, RF can identify the likelihood of occurrence for different levels of generation unavailability over the summer period (May through September). When comparing the last five years of historical generation unavailability that occur to varying levels of anticipated demand, which includes demand response and operating reserves, RF can identify risks associated with resource adequacy.

The chart below shows PJM’s summer outage likelihood based on different generation outage levels. The two yellow dots show the summer outage probability in the 50/50 demand forecast and the 90/10 demand forecast. The blue line represents three-year historic generation unavailability.

Since NERC’s normal resource unavailability, which only accounts for three years of average forced outages, reduces total resources in PJM to just above their 90/10 demand, the overall risk to the BPS is normal. However, RF has determined that there is higher probability for PJM to use load modifying resources under extreme demand.

Should the system encounter a scenario in which there is a combination of higher demand (i.e., 90/10) and/or higher generation outages that are above anticipated levels, PJM is still anticipated to be at normal risk for the upcoming summer season. As shown by the yellow dot on the left marking the 90/10 demand forecast, there is slightly less than a 50% probability of PJM experiencing outages totaling 15,000 MW, less than the historic average and therefore expected to be able to serve the forecasted 90/10 load.

MISO

When assessing MISO’s 50/50 demand forecast, MISO, similar to PJM, is projected to have adequate resources to serve normal electric demand in the upcoming summer season, including periods in which certain generation resources may become unavailable. MISO’s planning reserve margin requirement is set at 15% for the 2026 planning year, and its forecasted reserve margin is also above that requirement at 31.1%.