How to use this calculator
- Enter the battery nameplate energy and desired discharge power.
- Apply the usable depth of discharge.
- Enter one-way discharge efficiency.
- Add available charging power and a daily energy target.
#1304 · Energy & Environment Tool
Renewable PPA Storage Duration Calculator
Estimate how long a battery paired with or supporting a renewable PPA can discharge at a chosen power level. The calculator converts nominal storage energy into usable delivered energy after depth-of-discharge and discharge-efficiency losses. It also estimates recharge time and the portion of a daily contracted-energy target that one full discharge could cover.
Calculator
Battery deliveryFormula
Delivered usable energy = nominal MWh × depth of discharge × discharge efficiency
Duration = delivered usable MWh ÷ discharge MW
Duration = delivered usable MWh ÷ discharge MW
What the result means
Duration is the time the battery can sustain the entered power after the specified usable-energy adjustments.
This simplified estimate does not model state-of-charge limits, inverter clipping, degradation, auxiliary load, or a time-varying dispatch profile.
Example calculation
A 100 MWh battery at 90% depth of discharge and 95% discharge efficiency delivers 85.5 MWh. At 25 MW, duration is 3.42 hours.
Tips for better results
- Use one-way efficiency rather than round-trip efficiency.
- Set discharge power to the expected dispatch level.
- Reserve extra state of charge if the contract requires contingency headroom.
- Account for degradation over the PPA term.
Frequently asked questions
Should I use round-trip efficiency for storage discharge duration?
No. Use the one-way discharge efficiency because this calculation follows stored energy through discharge only.
Why is usable storage energy below the battery nameplate rating?
Depth-of-discharge limits and discharge losses reduce the energy that can be delivered to the grid or load.
Does the renewable PPA storage duration calculation result include taxes or financing?
No. The estimate excludes degradation and time-varying dispatch constraints. Add taxes, financing costs, incentives, and contract-specific charges separately when they apply.
Can I enter decimal values in this renewable PPA storage duration calculation?
Yes. Decimal inputs are supported, and the calculator keeps full precision until results are displayed.
What happens if I enter zero?
Zero is accepted where it represents a valid operating condition. A value that would make the formula undefined triggers an input message instead of showing an invalid result.
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Variables and units
| Variable | Meaning | Unit |
|---|---|---|
| Eₙ | Nominal battery energy | MWh |
| DoD | Usable depth of discharge | % |
| ηd | One-way discharge efficiency | % |
| P | Discharge power | MW |