Energy
Battery Runtime Calculator
Estimate how long a battery or inverter system can power a load using battery capacity, voltage, usable depth of discharge and system efficiency.
Battery
Ah
V
For a battery bank, enter the total bank Ah capacity at the bank’s nominal voltage.
Usable Capacity
%
%
Available capacity factor can account for aging, temperature or other derating. Leave at 100% for a new battery under rated conditions.
Load
W
Enter the average continuous power actually drawn by the connected appliances.
System Losses
%
%
Use 100% efficiency for a direct DC load if conversion losses do not apply. Reserve margin intentionally leaves some calculated usable energy unused.
Estimated Runtime
—
Estimated continuous runtime at the entered average load.
Nominal Battery Energy
—
Battery Energy Within DoD
—
AC / Load-Side Energy
—
Estimated DC Input Power
—
Estimated Conversion Loss
—
Runtime After Reserve
—
Runtime at Different Loads
| Load Level | Power | Estimated Runtime |
|---|---|---|
| 50% of entered load | — | — |
| 75% of entered load | — | — |
| 100% of entered load | — | — |
Methodology:
For an Ah-rated battery, nominal energy is estimated as
Ah × nominal voltage.
Usable battery energy is then adjusted for the entered
available-capacity factor and depth of discharge.
For an AC load, delivered energy is estimated by applying
inverter/conversion efficiency.
Runtime = delivered usable energy ÷ continuous load.
Actual runtime can differ because battery capacity depends on
chemistry, discharge rate, temperature, battery age, inverter
standby consumption, cut-off voltage and manufacturer limits.
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