SpecCalc Hub · Planning estimate
UPS Runtime Calculator
Estimate UPS runtime from battery configuration, load, efficiency, and usable capacity.
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0 h 29 min
Formula
battery_wh = voltage * Ah * count usable_wh = battery_wh * usable_capacity * efficiency runtime_hours = usable_wh / load_w load_percent = load_w / (VA * PF) * 100
Assumptions
- Inputs are user-provided.
- Results are preliminary estimates.
- Battery is healthy and load is constant.
Limitations
- Manufacturer runtime curves may differ significantly.
Sources / methodology
Uses battery Wh adjusted by usable capacity and efficiency.
- Formula version
- 1.0.6
- Formula review date
- 2026-05-25
Source links
Quick answer: UPS Runtime Calculator estimates battery energy from transparent input parameters and a visible formula. Results are informational estimates only and should be checked against the stated assumptions and limitations.
Input parameters
- Load (W): 300 W
- Battery voltage (V): 12 V
- Battery capacity (Ah): 9 Ah
- Battery count (pcs): 2 pcs
- UPS efficiency (%): 85 %
- Usable capacity (%): 80 %
- UPS rating (VA): 1,000 VA
- UPS power factor (PF): 0.6 PF
Output values
- Battery energy (Wh)
- Usable energy (Wh)
- Runtime (min)
- UPS load (%)
Step-by-step example
Calculation for the example inputs shown above:
- E₀ = 12 × 9 × 2 = 216 Wh
- E = 216 × 80% × 85% = 146.88 Wh
- t = 146.88 ÷ 300 × 60 = 29 min
- Load fraction = 300 ÷ (1,000 × 0.6) × 100% = 50 %
Use the manufacturer’s runtime curve for the final choice; battery discharge rate and cutoff voltage affect the actual time.
Worked examples
Worked example with the form defaults
Example inputs: Load: 300 W; Battery voltage: 12 V; Battery capacity: 9 Ah; Battery count: 2 pcs; UPS efficiency: 85 %; Usable capacity: 80 %; UPS rating: 1,000 VA; UPS power factor: 0.6 PF. E₀ = 12 × 9 × 2 = 216 Wh. E = 216 × 80% × 85% = 146.88 Wh. t = 146.88 ÷ 300 × 60 = 29 min. Load fraction = 300 ÷ (1,000 × 0.6) × 100% = 50 %. Use the manufacturer’s runtime curve for the final choice; battery discharge rate and cutoff voltage affect the actual time.
Alternative calculation scenario
Example inputs: Load: 200 W; Battery voltage: 12 V; Battery capacity: 9 Ah; Battery count: 2 pcs; UPS efficiency: 85 %; Usable capacity: 80 %; UPS rating: 1,000 VA; UPS power factor: 0.6 PF. E₀ = 12 × 9 × 2 = 216 Wh. E = 216 × 80% × 85% = 146.88 Wh. t = 146.88 ÷ 200 × 60 = 44 min. Load fraction = 200 ÷ (1,000 × 0.6) × 100% = 33.3 %. Use the manufacturer’s runtime curve for the final choice; battery discharge rate and cutoff voltage affect the actual time.
What the result does not establish
A 1000 VA label does not mean 1000 Wh of storage. Compare the estimate with the manufacturer’s runtime curve at the actual load, battery configuration and battery condition.
Common mistakes
- Keep all units consistent with the field labels.
- Check whether the input values are measured, nameplate values or planning assumptions.
- Review the stated assumptions and limitations before using the estimate.
What to check next
Check the inputs, limitations, sources and related calculators before using the estimate in a real decision.
FAQ
What does UPS Runtime Calculator calculate?
UPS Runtime Calculator estimates battery energy from transparent input parameters and a visible formula. Results are informational estimates only and should be checked against the stated assumptions and limitations.
What formula does this calculator use?
The visible formula starts with: battery_wh = voltage * Ah * count. The full formula, assumptions and limitations are shown on the page.
Are the results stored?
No account is required and SpecCalc Hub does not save personal calculation history.
Related calculators
This calculator provides an estimate for informational purposes only. It is not a certified engineering design, electrical safety approval, or professional installation recommendation. Always verify final decisions with a qualified professional and applicable local codes.