🔋 Battery Runtime Calculator for Electrical
Estimate runtime from capacity, voltage, load and usable depth.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the Battery Runtime calculator →
How to calculate battery runtime
Method: Runtime = amp-hours × voltage × usable fraction × efficiency ÷ load watts
- Convert nominal battery capacity to watt-hours.
- Apply a usable-capacity limit appropriate to chemistry and life target.
- Allow for conversion losses, then divide by average load.
Worked example
Using these planning inputs:
- Battery capacity: 100 Ah
- Nominal voltage: 12.8 V
- Average load: 300 W
- Usable capacity: 80 %
- System efficiency: 90 %
Estimated runtime: 3.07 h
Reality check: Age, temperature, discharge rate, inverter standby use and low-voltage cutoff can materially reduce runtime.
Method status and references
Energy-balance estimate. The conversion from amp-hours to watt-hours assumes the entered nominal voltage. Real delivery depends on chemistry, rate, temperature and cutoff behaviour.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.