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SESK: Stuff Everyone Should Know · sesk.info/solar-usable-capacity

A 10 kWh battery operating at a 90% depth of discharge has how much usable capacity?

9 kWh, since only 90% is used.

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  1. 10 kWh
  2. 9 kWh ✔
  3. 1 kWh

Why: Usable capacity is what a battery offers once practical limits apply. At 90% depth of discharge, a 10 kWh battery gives 9 kWh. That is why spec sheets list both nominal and usable numbers.

Huh, didn't know that: NREL's Storage Futures Study calls depth of discharge the opposite of state of charge.

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If you had 10 cookies and I asked you for three, how many would you have left? If you asked me? 10.
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References

Answer: 9 kWh. Usable capacity is what a battery offers once practical limits apply. At 90% depth of discharge, a 10 kWh battery gives 9 kWh. That is why spec sheets list both nominal and usable numbers.

  1. NREL: Storage Futures Study, Storage Technology Modeling Input Data Report docs.nlr.gov/docs/fy21osti/78694.pdf
    a 10-kWh battery that operates assuming a 90% depth of discharge has a usable storage capacity of 9 kWh
    Checked 2026-10-10.

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