Estimate UPS VA class and usable battery energy from load watts, desired runtime, power factor, UPS efficiency and battery voltage.
Results are for information and preliminary estimation. For critical technical work, manufacturer data, local codes and qualified professional review take precedence.
UPS VA ≈ load W / power factor × reserve. Battery energy ≈ load W × runtime / UPS efficiency. Real runtime depends on manufacturer curves and battery behavior.
Example: A 450 W computer with 25% headroom may need a UPS class above entry-level 600 VA models.
Computer and network tools provide practical capacity planning. Vendor limits, protocol overhead, codecs and real connection quality can move results away from theoretical values.
No; watts are real power while VA is apparent power, linked by power factor.
Battery voltage, discharge curve, inverter efficiency and high-current losses change runtime.
Tell us if a calculation is unclear, incomplete or appears incorrect.