---
title: "UPS Battery Backup Time Calculator"
description: "Free UPS backup time calculator: estimate how long batteries will run your servers, network, CCTV or POS, or the capacity needed for load-shedding."
url: https://utechit.pk/tools/ups-battery-backup-time-calculator
updated: 2026-09-27
publisher: UltraTech Pakistan
---

# UPS Battery Backup Time Calculator

Enter the load in watts and your battery bank's voltage, capacity and chemistry. The calculator estimates the runtime after inverter losses and safe depth of discharge. It also works out the battery capacity you need for a target backup time.

The interactive calculator is on the web page. AI agents can run the same calculation with the MCP server at https://utechit.pk/mcp.

## Frequently asked questions

### How do you calculate UPS backup time?

Backup time (hours) = battery voltage × capacity (Ah) × usable depth of discharge × inverter efficiency ÷ load (W). For example, a 24 V 200 Ah lithium bank at 90% usable and 90% efficiency runs a 500 W load for about 7.8 hours.

### Why is lithium usable capacity higher than lead-acid?

Lead-acid batteries last much longer if you use only about half their capacity, while lithium (LiFePO4) batteries can safely use about 80–90% on every cycle.

### Should I size for the whole office or just IT?

For the longest backup at the lowest cost, put only critical IT on the UPS: servers, network, CCTV and POS. Air-conditioning and heavy loads are better served by a generator or a separate solar system.

## Related service

- [UPS & Solar Backup for IT](https://utechit.pk/it-infrastructure-solutions/ups-solar-backup-for-it-systems-lahore): Keep servers, networks, CCTV and POS running through load-shedding

## Contact

- Email: info@utechit.pk
- Office: Shop B-2, FIJEL PLAZA, Block N, Valencia Town, Lahore, Pakistan
- Quotes are fixed and written; work outside the quote is not invoiced.