Battery Capacity Calculator
Convert battery voltage and amp-hours to watt-hours.
Formula
Battery energy in watt-hours = volts × amp-hours.
What Does Battery Capacity in Wh Mean?
Watt-hours estimate the electrical energy stored in a battery by combining its nominal voltage with amp-hour capacity. This makes batteries with different voltages easier to compare on an energy basis.
Example Calculation
A 12 V battery rated at 100 Ah has a nominal energy capacity of 12 × 100 = 1,200 Wh, or 1.2 kWh.
Factors That Affect Usable Energy
The calculated value is nominal. Actual usable energy can be lower because voltage changes during discharge, inverter losses, temperature, battery age, discharge rate and recommended depth-of-discharge limits affect performance.
Interpreting the Result
Wh describes energy capacity, not runtime by itself. Approximate runtime also depends on the connected load power and system efficiency.
Frequently Asked Questions
Is Ah the same as Wh?
No. Ah measures charge capacity, while Wh includes voltage and measures energy.
How do I convert Wh to kWh?
Divide watt-hours by 1,000.
Will a 1,200 Wh battery deliver exactly 1,200 Wh?
Not necessarily. Real usable energy depends on battery chemistry, operating conditions and system losses.
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Formula and Practical Limits
Battery energy in watt-hours is approximately voltage multiplied by amp-hours. Actual usable energy depends on discharge rate, cutoff voltage, temperature, aging, chemistry and conversion losses.