Battery Storage Capacity Accreditation Calculator

Apply capacity market accreditation logic to battery storage resources by combining duration tests, availability assumptions, and seasonal derates into a defensible accredited megawatt value.

Rated discharge power of the storage resource.
Continuous hours the battery can sustain nameplate power within warranty limits.
Equivalent availability or 1 − forced outage rate during the accreditation season.
Defaults to 4. Regulatory minimum run-time that must be met for full accreditation.
Defaults to 0%. Accounts for forecasted capacity loss from cell aging before augmentation.
Defaults to 0%. Additional derate applied during extreme weather tests.

Confirm final accreditation values with the market operator and update assumptions whenever rules, outage data, or augmentation plans change.

Examples

  • 150 MW battery, 4 h usable duration, 95% availability, 4 h obligation, 6% degradation, 3% temperature derate ⇒ Accredited capacity: 123.69 MW (82.46% of nameplate). Energy-limited factor: 100.00%; availability factor: 95.00%; residual derate: 91.82%.
  • 80 MW battery, 3 h duration, 92% availability, default optional fields ⇒ Accredited capacity: 55.20 MW (69.00% of nameplate). Energy-limited factor: 75.00%; availability factor: 92.00%; residual derate: 100.00%.

FAQ

What if augmentation is scheduled mid-season?

Model the lowest expected capacity before augmentation is installed. Accreditation audits typically require conservative assumptions until new modules are operational.

How should I treat hybrid resources?

For solar-plus-storage or wind-plus-storage hybrids, apply the battery accreditation logic to the storage component and combine it with the accredited value of the generation resource per market rules.

Can I reflect inverter limits?

Yes. If inverter ratings or interconnection limits are below battery nameplate power, substitute the lower limit for nameplate power so the accredited megawatts do not exceed deliverable capacity.

Does the calculator handle multi-day storage?

Markets with obligations longer than 10 hours often implement bespoke rules. Adjust the obligation hours input accordingly and confirm whether additional derates (for state-of-charge management or fuel constraints) apply.

Additional Information

  • Energy-limited factor compares usable duration to the obligation hours required by the market and caps accreditation accordingly.
  • Availability factor reflects outage-adjusted performance during peak seasons; provide the same metric you submit in your capacity filings.
  • Residual derate multiplies seasonal degradation and temperature adjustments to produce a conservative accredited value.

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