UPS Battery Capacity Calculator
The UPS battery calculator helps you determine the required battery capacity in amp-hours (Ah) and estimated runtime for running home appliances, gas boilers, Wi-Fi routers, and electronics during power outages.
Backup Runtime Results
How to use
- Select your appliances or input total load consumption in Watts.
- Choose battery system voltage (12V, 24V, or 48V).
- Set desired backup runtime hours or available battery Ah rating.
- Select battery chemistry: lead-acid AGM/GEL or Lithium Iron Phosphate (LiFePO4).
- Review recommended battery Ah capacity and runtime calculations.
How UPS Battery Sizing Works
Calculating backup battery capacity uses the formula: Ah = (Watts × Hours) / (Volts × Inverter Efficiency × Depth of Discharge).
- Inverter efficiency typically ranges between 80% and 90%
- AGM/GEL batteries should not be discharged past 50–60% DoD to preserve lifespan
- LiFePO4 lithium batteries safely deliver 90% or more usable depth of discharge
Frequently Asked Questions
How long will a 100Ah battery run appliances?
A 12V 100Ah LiFePO4 battery delivers ~1,100 usable watt-hours, enough to run a 100W load for approximately 11 hours.
Can I use a car battery for a home UPS?
It is not recommended. Car starter batteries release hydrogen fumes indoors and degrade rapidly under deep-cycle power outage conditions.
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