Battery Backup Time Calculation

The following procedure and formula will help you to calculate your UPS / INVERTER Battery Backup Time.

Formula:

Battery Backup time = (Battery volt * Battery Ah rating) / (Total watts on Load)

Example:

Battery = 12v 35Ah

Load = 20 watt CFL + 10 watt ADSL router = 30 watt

Then,

Battery Backup time = (12 * 32) / 30 = 14 hour

Note: This calculation shows only approximate value because there will be some loss of energy when converting 12v battery power to 220v through inverter.