🔋 Battery Sizing Calculator for Solar & Energy
Estimate nominal storage for a backup target.
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 Sizing calculator →
How to calculate battery sizing
Method: Nominal capacity = backup energy ÷ usable capacity fraction ÷ conversion efficiency
- List only loads that genuinely require backup.
- Multiply average simultaneous load by the required backup hours.
- Allow for conversion losses and preserve the manufacturer’s recommended reserve.
Worked example
Using these planning inputs:
- Average critical load: 0.6 kW
- Backup duration: 8 h
- Usable capacity: 90 %
- Conversion efficiency: 90 %
Nominal battery: 5.93 kWh
Reality check: Also confirm surge power, inverter output, battery temperature limits, chemistry and warranty conditions.
Method status and references
Energy-balance estimate. The result sizes nominal energy only; it does not prove power, surge, thermal or lifecycle suitability.
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.