Skip to main content
Calcimator

Battery Capacity Calculator

Calculate amp-hours and watt-hours needed from load and runtime.

Inputs

W
hrs
V
%
%
%

Results

Required Capacity

122 Ah

Required Capacity

5.8 kWh

≈ 6 loads of laundry

Load Energy4,211 Wh
Battery Energy (with losses)5,848 Wh
How to Use This Calculator
  1. Enter Load Power, Required Runtime, and System Voltage.
  2. Set Max Depth of Discharge, Inverter Efficiency, and Temperature Derating.
  3. Review Required Capacity (Ah) and Required Capacity (kWh).
  4. Use Load Energy (Wh) and Battery Energy (with losses) (Wh) to inform your decision.

How the result changes with Load Power

Load PowerRequired CapacityRequired Capacity
5,0011,219 Ah58.5 kWh
17,5014,264 Ah204.7 kWh
32,5007,919 Ah380.1 kWh
45,00010,965 Ah526.3 kWh

What each input means

Load Power
Total continuous load in watts.
Required Runtime
Hours of backup runtime needed.
System Voltage
Battery system voltage.
Max Depth of Discharge
Maximum safe discharge level for the battery type.
Inverter Efficiency
DC-to-AC inverter efficiency.
Temperature Derating
Capacity reduction due to cold temperatures.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Load Power = 500, Required Runtime = 8, System Voltage = 48, Max Depth of Discharge = 80 = 6 input(s) provided
  2. Calculate Required Capacity
    Required Capacity
    122 = 122
  3. Calculate Required Capacity
    Required Capacity
    5.8 = 5.8
  4. Calculate Load Energy
    Load Energy
    4211 = 4211
  5. Calculate Battery Energy
    Battery Energy
    5848 = 5848

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Battery Storage

Battery Cycle Life Calculator

Estimate expected battery cycles from depth of discharge and chemistry.

Battery Storage

Battery C-Rate Calculator

Calculate charge and discharge time from battery C-rate.

Solar Energy

Solar Battery Sizing Calculator

Calculate battery storage capacity needed for solar backup.

Electrical Engineering

Battery Bank Sizing Calculator

Size a battery bank: calculate series/parallel configuration, total batteries, and usable capacity for off-grid and backup systems.

Electrical & Plumbing

Amps / Watts / Volts Converter

Convert between amps, watts, and volts. Enter any two values to calculate the third, plus energy cost estimates.

More in Energy & Utilities.