Eaton UPS Runtime Calculator

Calculator Inputs

UPS model or series

Running load watts

Running load VA

Power factor

UPS watt rating

UPS VA rating

Battery bus voltage

Internal battery amp hours

External battery amp hours

Parallel battery strings

Battery hour rating basis

Depth of discharge percent

Inverter efficiency percent

Battery age capacity percent

Temperature capacity percent

Safety margin percent

Peukert exponent

Example Data Table

Example	Load	Battery Setup	Efficiency	Age Capacity	Estimated Use
Network closet	350 W	48 V, 9 Ah, 2 strings	88%	95%	Router and switches
Small server	650 W	72 V, 9 Ah, 2 strings	90%	90%	Controlled shutdown
Storage rack	1100 W	96 V, 9 Ah, 3 strings	91%	85%	Short bridge time

Formula Used

The calculator estimates runtime from stored battery energy and adjusted load demand.

Raw battery energy: Battery voltage × total amp hours.

Total amp hours: Internal Ah plus external Ah, multiplied by battery strings.

Adjusted usable energy: Raw Wh × discharge limit × efficiency × age factor × temperature factor × Peukert factor.

Runtime hours: Adjusted usable Wh ÷ load watts with safety margin.

The Peukert factor reduces available capacity when discharge current is high. This makes the estimate more realistic for heavy UPS loads. Use the official Eaton runtime chart when exact model performance is required.

How To Use This Calculator

Enter the real running watts for connected equipment. Add VA and power factor when those values are available. Enter the UPS watt and VA ratings to check load utilization.

Next, add the battery voltage, amp hour rating, external pack capacity, and number of parallel strings. Adjust the efficiency, battery age, temperature, depth of discharge, safety margin, and Peukert exponent. Press the calculate button. The result will appear above the form and below the header.

Use CSV export for spreadsheets. Use PDF export for service records, audits, and maintenance reports.

Understanding Eaton UPS Runtime

An Eaton UPS protects equipment when utility power fails. Runtime tells you how long the connected load may stay online. The value is never fixed. It changes with battery size, battery age, room heat, inverter losses, and the actual watts used by devices.

This calculator gives a planning estimate. It does not replace the official runtime chart for a specific unit. It helps you compare loads before adding servers, network switches, cameras, or storage gear. You can also test how an older battery reduces backup time.

Why Accurate Load Matters

Many users enter only the printed VA rating. That can overstate runtime. Real runtime depends on watts. A low power factor may increase apparent load, but watts drain the battery. For best results, measure the running watts with a meter. Add only equipment that must stay on during an outage.

Battery Conditions Matter

UPS batteries are usually rated in amp hours. That rating is often based on slow discharge. A UPS discharge is faster. Peukert adjustment lowers capacity when current is high. Heat, cold, and aging also change capacity. A battery that looks normal may deliver much less energy near replacement time.

Planning Better Backup

Use the safety margin field for conservative planning. A larger margin is useful for critical routers, medical office systems, point of sale equipment, and recording devices. It also helps cover startup changes, unknown adapters, and small future additions.

When the result is short, reduce load first. Remove monitors, printers, chargers, and nonessential accessories. Then consider extra battery packs or a larger UPS. Runtime should match the shutdown plan. Five minutes may be enough for automatic shutdown. Longer runtime is better for network continuity.

Reading the Output

The result shows adjusted watt hours, estimated minutes, load current, and utilization. Utilization warns when the UPS rating is close to the load. A high utilization can cause alarms or overload trips. Keep headroom where possible.

Save the CSV for spreadsheets. Use the PDF report for maintenance notes. Recheck the estimate after battery replacement, equipment changes, or seasonal temperature shifts. For shared equipment closets, record each device name and plug count. Clear records make audits easier. They also help teams justify maintenance budgets during reviews.

FAQs

Is this an official Eaton runtime chart?

No. It is a planning calculator. It uses common battery energy formulas and adjustment factors. Use Eaton model documentation for guaranteed runtime values.

Should I enter watts or VA?

Enter both when possible. Watts control battery drain. VA helps check UPS loading. The calculator uses the larger derived real load for safer estimation.

What is battery age capacity?

It estimates lost battery capacity over time. A new battery may be near 100 percent. An older battery may be far lower, even if the UPS still runs.

Why does Peukert exponent matter?

Battery capacity falls during fast discharge. UPS loads can draw high current. The Peukert exponent reduces available energy to reflect that effect.

What safety margin should I use?

Use 10 to 20 percent for normal planning. Use a higher margin for critical systems, older batteries, uncertain loads, or future equipment additions.

Can this include external battery packs?

Yes. Add the external amp hour value in the external battery field. Keep voltage and string assumptions consistent with the actual battery setup.

Why is my estimated runtime low?

The load may be high, batteries may be small, or age and temperature factors may reduce capacity. Lower nonessential load first.

Can I save the calculation?

Yes. Use the CSV button for spreadsheet records. Use the PDF button after calculation to save a simple maintenance report.