Furseka CalcReal-life calculatorsby FurrySekai

Power & battery

How long can a battery run my equipment?

Calculate runtime for a UPS, power-station fridge, laptop, CCTV system, or custom equipment from Wh, load, losses, and battery condition.

Formula version 1.0.0 · Last reviewed 2026-08-30

Preparing the calculator.

Calculator inputs and results

UPSEstimate outage backup time from UPS battery energy and connected load.

Example inputs

These values are examples. Replace them with product-label or measured values before calculating.

Prefer a verified Wh value. Use voltage and Ah together only when Wh is unavailable.
Wh
W
Battery condition, losses, and additional settings
%
Current full-charge capacity as a percentage of new capacity.
%
Share available before protection cutoff and your planned reserve.
%
Losses between the battery and equipment, including inverter or DC conversion.
W
VA
VA is an output rating, not stored battery energy in Wh.

Ready when you are

Choose a profile, check the battery and load, then calculate the estimated runtime and range.

Formula and assumptions

Read the baseline with the usage-variation range. Instantaneous output conditions such as UPS watt rating and refrigerator startup surge remain separate from energy duration and appear as checks.

Usable energy (Wh) = rated battery energy × health × usable share × conversion efficiency. Divide usable energy by the selected equipment's total average watts. A fridge can use measured average power or running watts times duty cycle; CCTV sums every component load.

Why the result can vary

Battery age, temperature, inverter loss, workload, fridge door opening, PoE loss, and protection cutoff all change real runtime.

Example

Compare equipment time during an outage

Inputs: 1,000Wh power station, 95% health, 90% usable, 90% efficiency, 100W average load

Outcome: About 770Wh remains usable, giving roughly 7.7 hours plus a practical range.

Cautions

  • Prefer product-label energy and measured average load over example values.
  • Overload, startup surge, and battery damage are safety conditions separate from the runtime estimate.
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Frequently asked questions

How many hours will a UPS battery last in an outage?

You need battery Wh and actual connected watts. VA is an output rating rather than stored energy, so enter Wh or voltage×Ah and verify the UPS watt rating separately.

How long can a power station run a refrigerator?

Measured average watts are best. If you only know compressor-on watts, enter a duty cycle and separately confirm that startup surge stays below the power station output limit.

Can laptops and CCTV use the same runtime method?

Yes. Stored energy divided by average load is shared, while laptop battery health and workload or the full CCTV equipment load are handled by their own profiles.