DailyHub

UPS & battery backup calculator

Estimate how long your UPS batteries will run your fans and lights during load-shedding.

e.g. 3 fans (≈80 W each) + 4 LED lights (≈15 W each).
Lead-acid ≈50%, lithium ≈80–90%.
How it's calculated

Hours = Ah × V × batteries × usable% × inverter efficiency ÷ load W.

  • Lead-acid typically 50% usable, lithium 80–90%
  • Battery age and temperature reduce capacity

Version 1.0 · exact decimal maths · inputs are not stored.

Questions

Why only 50% usable capacity?

Regularly draining lead-acid batteries below about half charge shortens their life sharply. Lithium batteries tolerate 80–90%.

How do I reduce the load?

Use DC inverter fans and LED lights, and avoid running irons, kettles or ACs on battery power.