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POWER BACKUP, MADE CLEAR
UPS Calculator for your load.
Check watt and VA capacity, allow for future load, and explore indicative battery energy for your backup time.
Plan your backup capacity.
Add the running watts of equipment that needs backup. Use measured or data-sheet values.
Use the load’s measured or specified power factor. 0.9 is an assumption, not the UPS rating.
Examples are a starting point. Replace them with your equipment; up to 12 items.
Extra load you want the UPS and battery estimate to allow for.
80% leaves capacity headroom. Both watt and VA ratings must support this target.
Time you want the design load to run during an outage. Battery discharge data must confirm it.
Battery assumptions
Generic energy assumptions only. Actual capacity depends on the selected battery, discharge rate, temperature and age.
Share of battery energy converted to useful AC output. Use the selected UPS data.
Share of nominal battery energy allowed for discharge. Use your battery/design limit.
Capacity retained after age, temperature and discharge-rate allowances. This does not replace a runtime curve.
Live estimates stay in this tab. Contact details are shared only when you request a report.
Your backup requirements, explained.
The first submission is checked on our server. Further edits update this private on-screen preview instantly.
Live preview updated from your current values. The original enquiry remains saved; these edits stay in this tab unless you email an updated PDF.
Inputs & assumptions
Calculated results
Required nominal battery energy
These are energy estimates at the design load. They are not battery discharge curves or model-specific runtime guarantees.
How the numbers are calculated
Equipment breakdown
| Equipment | Quantity | W each | Power factor | Total W | Total VA |
|---|
POWER BACKUP, MADE CLEAR
Know what the ratings mean.
Watts describe real power; VA describes apparent power. A suitable UPS must meet both requirements. Battery energy is a separate estimate and does not confirm a model’s actual runtime.
Why are both watts and VA shown?
UPS units have separate W and VA output limits. The load power factor relates equipment watts to VA, but the chosen UPS has its own rating limits. A common VA size is only a starting point; confirm that its watt rating also meets the calculation.
What do growth and target loading do?
Growth adds an allowance to the current equipment load. Target loading then leaves additional capacity headroom in the UPS ratings. For example, 80% target loading means the design load should use no more than 80% of the selected output ratings.
Is the battery estimate a guaranteed backup time?
No. It is a nominal-energy estimate based on design watts, runtime, efficiency, usable fraction and capacity allowance. Battery discharge rate, chemistry, temperature, age and the UPS itself affect actual runtime. Use manufacturer discharge curves to confirm it.
Can I include motors or other starting loads?
Running watts alone may not capture starting surge or other load characteristics. Phase, topology, inrush and compatibility need an engineering check. This tool does not select a battery voltage, bank arrangement or a particular UPS model.
Reference: Eaton UPS sizing guide. Confirm the final selection and runtime against manufacturer data.