How to use this calculator
- Enter project values using the units shown beside each field.
- Select Calculate to update the main estimate and supporting results.
- Review the interpretation and test realistic high and low assumptions.
#1019 · Energy & Environment Tool
Utility Solar Storage Duration Calculator
Estimate utility-scale battery discharge duration from nameplate energy, usable fraction, efficiency, and scheduled export power.
Calculator
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Formula
Duration (hours) = nameplate energy × usable fraction × delivery efficiency ÷ discharge power
What the result means
The result estimates how long the battery can maintain the specified export power using its modeled deliverable energy.
This simplified energy balance excludes state-of-charge reserves, degradation guarantees, HVAC and auxiliary consumption, ramping, and inverter overload limits.
Example calculation
A 400 MWh battery with 90% usable energy and 92% delivery efficiency provides 331.2 MWh. At 100 MW, duration is 3.31 hours.
Tips for better results
For contract evaluation, use guaranteed end-of-life energy and the precise point-of-interconnection power rather than beginning-of-life nameplate ratings.
Keep units and AC/DC or gross/net definitions consistent across every input.
Frequently asked questions
What does this utility solar storage duration estimate show?
The result estimates how long the battery can maintain the specified export power using its modeled deliverable energy.
Can I use this result for a final investment or engineering decision?
No. Use it as a screening estimate and confirm project-specific assumptions with qualified engineering, financial, utility, and tax professionals.
Why might actual results differ?
Weather, equipment performance, outages, degradation, curtailment, tariffs, operating strategy, and data-basis differences can all change actual outcomes.
Should I use AC or DC solar capacity?
Use the capacity basis specified by the input label and keep every production or performance value on the same basis.
How often should I update the estimate?
Update it whenever design ratings, resource studies, operating data, tariffs, incentives, battery condition, or project costs change.
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Quick reference
| Item | Guidance |
|---|---|
| Best use | Early-stage screening and scenario comparison |
| Update when | Design, resource, cost, tariff, or operating assumptions change |
| Decision quality | Confirm with project-specific engineering and financial analysis |