Battery Depth of Discharge Calculator
Depth of discharge is the difference between a battery’s starting state of charge and its chosen reserve. This estimator applies an efficiency factor to estimate energy delivered over that operating window.
How to use this calculator
- Enter reserve SOC no higher than the starting SOC and use a measured or documented efficiency assumption.
- Check that the input values use the same units and reporting period before comparing scenarios.
- Change one assumption at a time to see which input drives the result.
Formula and method
Depth of discharge (%) = starting SOC − reserve SOC; delivered energy ≈ rated capacity × DoD share × discharge efficiency.
- DoD = 80%; nominal energy removed = 13.5 × 0.8 = 10.8 kWh; delivered estimate = 9.936 kWh.
- Usable capacity changes with temperature, battery age, power draw, chemistry, safety limits and inverter losses. Follow the manufacturer’s limits.
Worked examples
Worked example
A 13.5 kWh battery moves from 100% to a 20% reserve, at 92% assumed discharge efficiency.
DoD = 80%; nominal energy removed = 13.5 × 0.8 = 10.8 kWh; delivered estimate = 9.936 kWh.
The scenario delivers about 9.94 kWh before other system losses.
Understanding the result
The scenario delivers about 9.94 kWh before other system losses.
Usable capacity changes with temperature, battery age, power draw, chemistry, safety limits and inverter losses. Follow the manufacturer’s limits.
Important notes
Enter reserve SOC no higher than the starting SOC and use a measured or documented efficiency assumption.
The displayed result uses the entered assumptions; validate important estimates against source measurements, specifications or qualified guidance.
Frequently asked questions
Is depth of discharge the same as state of charge?
No. SOC is remaining charge level; DoD is the portion used from the starting level.
Does this predict battery life?
No. Cycle life depends on chemistry, temperature, charge rate and many other factors.
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Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.