Grid-Scale Battery Energy Storage Systems worked example

BESS Capacity Gap at 68% system availability: a worked example

Suppose system availability falls to 68%. This page works the full calculation at that level so you can see exactly which result moves and by how much. Calculate net usable MWh capacity for a grid-scale BESS project by combining usable MWh per container, container count, system availability, and round-trip efficiency to identify the gap between gross nameplate and achievable delivered energy.

The inputs for this scenario

  • Usable MWh per BESS container: 4 MWh / container (held at the documented default)
  • Number of BESS containers in the project: 50 containers (held at the documented default)
  • System availability: 68 % (the input this scenario stresses; the baseline uses 95)
  • Round-trip efficiency: 87 % (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Gross BESS project capacity = usable MWh per container x number of BESS containers.
  • Net deliverable BESS MWh (availability and RTE adjusted) works out to 118 units at these inputs, and this is the headline figure for the scenario.
  • Gross BESS project nameplate capacity (MWh) works out to 200 units at these inputs.
  • MWh lost to system availability deduction works out to 64 units at these inputs.
  • MWh lost to round-trip efficiency losses works out to 17.68 units at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where system availability sits at 95% and the headline result is 165 units, this scenario comes in 28.42% below the baseline at 118 units.
  • It multiplies usable container energy by container count for gross nameplate, then derates by availability and round-trip efficiency to get net deliverable MWh. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Net deliverable BESS MWh (availability and RTE adjusted): 118 units (headline result)
  • Gross BESS project nameplate capacity (MWh): 200 units
  • MWh lost to system availability deduction: 64 units
  • MWh lost to round-trip efficiency losses: 17.68 units

Run it with your numbers

  • To rerun this with your own numbers, open the live BESS Capacity Gap calculator, set system availability to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.