CAISO Summer 2019 Weather Outlook

On May 8, 2019, the California Independent System Operator (CAISO) published its 2019 Summer Loads & Resources Assessment, which is the assessment report of the upcoming summer supply and demand outlook within the CAISO balancing authority area. The CAISO uses a stochastic production simulation model to run possible scenarios for load and generation. While historical weather data is used, the CAISO also relies on information from state agencies, generation and transmission owners, load serving entities, and other balancing authorities. Highlights from the recently released report are provided below.

The CAISO 2019 1-in-2 (base case) forecasted gross load peak demand is 46,511 MW, which is slightly below the 2018 weather normalized peak demand. The slight decrease in the demand projection is “a result of projected modest economic growth over 2018” and “reduced by ongoing behind the meter solar installations and energy efficiency program impacts on peak demand”. The CAISO 2019 1-in-10 peak demand forecast is 48,979 MW.

As of April 2, 2019, California hydro conditions for 2019 were “above normal”, registering a statewide snow water content in the mountain regions of 162 percent of the April 1 average. Additionally, major statewide reservoir storage levels were at 109% of normal, on an average basis. Such conditions will likely lead to hydro oversupply conditions going into this summer.

The CAISO projects 51,765 MW of system capacity for the summer, using the final net qualifying capacity (NQC) list that was used for the California Public Utilities Commission (CPUC) and CAISO’s resource adequacy program for the 2019 compliance year. There is a total of 1,523 MW from new generation interconnected to the CAISO balancing authority area which has come online within the past twelve months. Solar (640 MW) and gas (554 MW) experienced the most amount of new generation, followed by wind (156 MW).

As new renewable resources have entered the system, CAISO reliability requirements have “evolved from meeting the gross peak demand to meeting both net peak demand and flexible capacity requirements”. The summer outlook assessment states that the gross peak usually occurs at the hour ending of 16:00 or 18:00 while net peak occurs in the hour ending 19:00 to 21:00 timeframe, when solar generation is close to zero. The continual growth of photovoltaic solar generation interconnected to the CAISO grid continues to change the CAISO’s net load profile and “create more challenges and uncertainty for CAISO operations”.

There is still uncertainty surrounding the state of the Southern California natural gas system. The gas system “continues to operate at less than full capacity due to pipeline outages and continuing restrictions on use of the Aliso Canyon natural gas storage facility”. System-wide outages are expected to continue throughout much of the summer. It is worth noting that the reliability risk related to the Aliso Canyon and related gas storage facilities is greater in Southern California as opposed to the CAISO system as a whole. From a system perspective, the CAISO states that “the risk to electric reliability and the ability to re-supply from electric supply sources not impacted by SoCalGas limitations is similar to previous years”.

Projections for summer 2019 demonstrate there is “less risk of encountering operating conditions that could result in operating reserve shortfalls than was projected for 2018”, which is primarily a result of greater than average hydro conditions. The greatest operational risk facing the CAISO footprint is hot weather extending to neighboring balancing authority areas in late summer and weakening the import of load during high peak conditions. With hydro availability declining and solar production ramp-down beginning earlier in the afternoon, the late summer period experiences an increased reliance on load imports to ensure system reliability.

Even with CAISO’s robust prediction models and forecasts, Californians are encouraged to continually monitor weather and fire trends during the upcoming summer months, as well as appropriately respond to Flex Alert warnings and guidance. Visit the CAISO website for up-to-date system information and notices.