Use this battery backup calculator to calculate estimate battery runtime from capacity, voltage, load, efficiency, and depth of discharge.
battery backupruntimecapacityinverter
Calculator
Calculate instantly
Calculator Inputs
Choose what you want to calculate, enter realistic values, adjust units where shown, and use the scenario section for repeated-use planning.
Input and Formula Breakdown
This calculator applies the formula Runtime = Ah x V x DoD x efficiency / load. Enter each value with the matching unit, and AZCalculate updates the result instantly.
Battery capacity
200 Ah
Battery voltage
12 V
Depth of discharge
80 %
System efficiency
90 %
Load
500 W
Runtime
3.46 hours
Usable energy
1,728 Wh
Scenario and Comparison
Current
3.46 hours
Projected
41.47
Adjusted
3.8
Visual Comparison
Current result3.46
Projected usage41.47
Comparison scenario3.8
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Use this result as a practical estimate. Real-world conditions, local rules, measurement tolerance, and changing inputs can affect the final outcome.
Medium risk contextDifficulty: professionalConfidence estimate: 95/100Reviewed 2026-05-18Reviewed by: Engineering content reviewerCalculator vuces-2.1 / Formula vformula-1.03 sources listed
Formula and Explanation
Runtime = Ah x V x DoD x efficiency / load
This calculator applies the formula Runtime = Ah x V x DoD x efficiency / load. Enter each value with the matching unit, and AZCalculate updates the result instantly.
Variable descriptions
capacity(Ah)
Battery capacity: Battery capacity measured in Ah, entered as a known value.
voltage(V)
Battery voltage: Battery voltage measured in V, entered as a known value.
dod(%)
Depth of discharge: Depth of discharge measured in %, entered as a known value.
efficiency(%)
System efficiency: System efficiency measured in %, entered as a known value.
load(W)
Load: Load measured in W, entered as a known value.
Formula Notes
Use consistent units for values that are multiplied, divided, or compared.
Results may be rounded for readability, while the calculator keeps greater precision internally.
Real-world measurements and assumptions can introduce small differences from the calculated estimate.
Common uses
•Plan backup power
•Size batteries
•Compare runtime scenarios
Assumptions
What this calculation assumes
Calculations assume compatible engineering units and idealized conditions.
Safety factors, tolerances, material variation, and standards should be reviewed separately.
Inputs are assumed to describe the same scenario and use compatible units.
Results may be rounded for readability.
Avoid mistakes
Quick checks before you rely on the result
Ignoring safety factors.
Using rated values instead of actual operating conditions.
Mixing units, periods, currencies, or measurement systems without converting first.
Rounding intermediate values too early.
Step-by-Step Explanation
Follow the reasoning, not only the final number.
1
Set up the calculation
Enter the known values in the calculator fields.
Starting with clearly defined values and units prevents the most common calculation errors.
2
Work through step 2
Keep the units consistent with the labels shown beside each input.
This step transforms the known values into the form required by the formula.
3
Work through step 3
Apply the formula: Runtime = Ah x V x DoD x efficiency / load.
This step transforms the known values into the form required by the formula.
4
Interpret the result
Review the primary result and supporting values.
Compare the result with your real-world goal, such as plan backup power.
Worked example
Practical battery backup calculator example
Known values
Battery capacity: 200 Ah
Battery voltage: 12 V
Depth of discharge: 80 %
System efficiency: 90 %
Load: 500 W
Calculation
1. Start with the known values shown for this battery backup calculator scenario.
2. Substitute those values into Runtime = Ah x V x DoD x efficiency / load.
3. Evaluate the expression and keep the requested unit and rounding.
Result and meaning
Runtime: 3.46 hours; Usable energy: 1,728 Wh
Calculator guide
About this Battery Backup Calculator
Estimate battery runtime from capacity, voltage, load, efficiency, and depth of discharge. This page includes an interactive calculator, concise formula notes, worked examples, FAQs, related calculators, and practical guidance you can revisit whenever needed.
We work hard to keep every calculator accurate and useful. If you notice a calculation error, missing option, or unclear explanation, please let us know so we can review and correct it promptly.
