Small Modular Reactor Capacity Credit Calculator

Estimate accredited capacity for a small modular reactor by applying forced outage, maintenance, and seasonal temperature derates to nameplate output.

Gross electrical nameplate of the SMR block or multi-module site.
Expected forced outage percentage used in capacity accreditation.
Seasonal or scheduled derating factor; defaults to 5% when blank.
Net capacity reduction during peak temperature events; defaults to 3% when blank.

Screening aid only. Align final capacity accreditation with market operator rules and probabilistic reliability studies.

Examples

  • 320 MW nameplate, 4.5% forced outage, 5% maintenance, 3% temperature derate ⇒ Accredited capacity 286.44 MW (89.51% of nameplate).
  • 77 MW nameplate, 3% forced outage, maintenance left blank (defaults 5%), temperature derate left blank (defaults 3%) ⇒ Accredited capacity 69.99 MW (90.89% of nameplate).

FAQ

Why apply both maintenance and temperature derates?

Resource adequacy studies must reflect summer peaks when maintenance might overlap with seasonal heat limits; using both provides a conservative credit.

Can multi-module sites use lower forced outage rates?

Module diversity can lower effective outage rates, but use regulator-approved values or empirical fleet averages when available.

How should uprates be handled?

Apply uprated nameplate capacity and reassess derate assumptions; if uprates add heat rejection stress, increase the temperature derate accordingly.

Additional Information

  • Result unit: accredited capacity in megawatts and as a percent of nameplate.
  • Maintenance derate defaults to 5% to reflect typical rotating outage sharing across modules.
  • Temperature derate defaults to 3% to account for condenser performance in high ambient conditions.

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