There are three types of reserves: planning, balancing, and contingency:

  • Planning reserves are held to respond to uncertainties such as anticipated growth in demand for electricity and river conditions that affect the output of hydropower generation (lower than normal river conditions can mean lower hydropower generation). Thus, planning reserves account for year-to-year variation in generation and load.
  • Balancing reserves are held for short-term uncertainties such as the ups and downs of wind power generation and seasonal demand for power – summer air conditioning, winter heating, for example. Balancing reserves also are held to account for any errors made in forecasting load and generation on an hour-to-hour basis.
  • Contingency reserves are held to respond to unexpected transmission system or power plant outages. Contingency reserves are part of what makes up operating reserves.

All of these reserves are incorporated into the calculation of additional resource requirements to maintain the Council’s adequacy standard[1] throughout the planning period.

Operating Reserves

TypeAmount Held
Balancing Up2,900 megawatts
Balancing Down3,345 megawatts
Contingency Reserves3% of load and 3% of generation

In both of the Council’s hourly models[2], dispatch of generation is dynamically co-optimized between energy and reserves and contingency reserves as[3] described in the table above are held in all hours. are The Council does not currently have a way to forecast balancing reserve needs going forward, so several different data sources are used for different purposes. For the wholesale electricity price study work in AURORA, reserve data was sourced from the 2026 WECC Common Case[4] due to the desire to assign reserve by operating pool[5].  Per multiple discussions in the February and March 2021 System Analysis Advisory Committee meetings, for all the redeveloped GENESYS simulations, the Northwest regional reserve requirements was the sum of the maximum regional balancing reserves[6] held by any balancing authority as shown in the table above.

Thus, by incorporating these reserves into the GENESYS modeling used to support the Adequacy Reserve Margin, the Associated System Capacity Contribution and expected hydro generation and in the wholesale electricity prices from the AURORA model that all feed into the Regional Portfolio Model, the treatment of reserves is implicit in the simulations that support the resource strategy analysis.

[1] 5 percent Loss of Load Probability

[2] AURORA and GENESYS

[3]Simplified interpretation of the Northwest Power Pool Reserve Sharing Agreement contingency reserve calculation.  See page 43 Attachment A. https://www.nwpp.org/private-media/documents/NWPP_RSG_Program_Documentation_-_RSG_Approved_2022_0112.pdf

[4] See https://www.wecc.org/SystemAdequacyPlanning/Pages/Datasets.aspx for more details on the Common Case

[5] For computational expediency, per discussion in April 2019 System Analysis Advisory Committee meeting.

[6] Same regional reserve source as Seventh Power Plan - a public data set from the Northwest Power Pool EIM effort.

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