UPS battery sizing
Estimate nominal battery energy and amp-hours from load, runtime, inverter efficiency and usable capacity.
Enable JavaScript for live calculations. Read the method and default example below.
Method and assumptions
- DC energy = AC load × runtime / inverter efficiency. Nominal energy includes the entered reserve and usable fraction.
- Ah = nominal energy × 1000 / nominal DC voltage.
Before using the result
- Energy budget only, not an IEEE 485 battery selection. Verify discharge-rate curves, minimum DC voltage, aging, temperature, BMS limits, fault protection and actual UPS compatibility. No battery life or breaker rating is predicted.
Worked example
Illustrative default inputs. Enter your project values above.
- AC load
- 5 kW
- Backup time
- 30 min
- Nominal DC bus voltage
- 48 V DC
- Battery chemistry
- VRLA
- Inverter efficiency
- 92 %
- Usable nominal capacity
- 50 %
- Energy reserve
- 20 %
Default results
- Nominal energy budget
- 6.52 kWh
- Nominal amp-hour budget
- 135.9 Ah
- Continuous DC current estimate
- 113.2 A
Choose a reference or send your BOQ
Compare relevant product families, then confirm the exact rating, control supply and duty. Price and availability are confirmed with your enquiry.
Technical references
These references support planning. The exact model documentation and a project-specific engineering review govern the final specification.