UPS Runtime Calculator: Estimate Backup Time by Load
Tell us your equipment load and required runtime. We'll show every UPS in our catalogue that fits, with the estimated runtime at your specific load.
Find a UPS that fits your load
Drag the slider to your equipment's wattage. Pick a minimum runtime. We'll rank the UPS units in our catalogue by how well they match.
Power factor 0.80 VA × power factor = real load in watts. Default 0.8 covers most modern IT gear.
Advanced settings
Recommended UPS units
Sorted by best fit. UPS units sized to run at 60-80% of capacity get top placement.
No UPS in our catalogue meets that load and runtime requirement. Try a smaller load, a shorter runtime, or contact a specialist for an engineering assessment.
Complete your setup
Accessories that pair with the recommended UPS. Model-specific accessories are listed on each product page.
UPS Runtime Calculator: enter your UPS capacity (VA or kVA) and connected load (watts) to estimate expected backup time during a power outage. Useful for sizing replacement batteries, planning generator-bridge time, and validating manufacturer-specified runtimes against real-world load.
How to Use the Calculator
- Find your UPS capacity: printed on the UPS nameplate, typically in VA (e.g. 1500VA) or kVA (e.g. 10kVA). Convert if needed: 1 kVA = 1000 VA.
- Estimate your connected load in watts: add up the wattage of every device plugged into the battery-backup outlets. Servers, monitors, switches, NAS, etc. Most equipment lists draw on the back-panel sticker.
- Enter both values above and the calculator returns expected runtime at that load. As a rule of thumb: full load = 5–15 minutes; half load = 15–40 minutes; quarter load = 1+ hour on standard internal batteries.
Sizing Tips
- Add 25% headroom to your real load when sizing a new UPS: this leaves room for equipment changes and prevents overload trip.
- Match VA to wattage carefully: a 1500VA UPS typically delivers only ~900W continuous (power factor ~0.6–0.7 for older units, ~1.0 for modern Smart-UPS / Eaton 9PX). Wattage is what matters for sizing real loads.
- For longer runtimes, add an external battery cabinet (most online UPS units support this) rather than oversizing the UPS frame itself.
- For loads that will grow, consider a modular UPS platform, capacity and N+1 redundancy scale by adding power modules instead of replacing the unit.
- For mission-critical loads, size to bridge generator startup (typically 8–12 seconds) plus a defensive buffer, the UPS is the bridge, not the long-duration backup.
- Battery age matters: by year 4 a VRLA battery typically delivers ~70% of nameplate capacity. Schedule replacement at year 3.5–4 in 24/7 deployments, see our UPS battery replacement service.
Related Resources
- UPS Battery Cross-Reference & Finder: replacing a battery instead of the UPS? Find the exact fit by model or RBC number
- Modular UPS Systems Guide: scalable frames, hot-swap modules, and the N+1 math
- UPS FAQ: single-phase vs three-phase, medical-grade, sizing
- UPS Battery FAQ: lifespan, replacement, compatibility
- Battery Technical FAQ: SLA / VRLA basics, V/Ah matching
- All UPS Replacement Batteries: our own compatible cartridges for APC RBC, Eaton 744-series, Vertiv GXT and Tripp Lite RBC units
- Line-Interactive vs Online UPS: topology decision guide
- Single-Phase Smart UPS Comparison: APC vs Eaton vs Vertiv selection
Need Help Sizing Your UPS?
If your environment is mission-critical: healthcare, data centre, mining, government IT, a calculator is a starting point but a proper site survey beats it. Our team handles full UPS installation and consulting with site assessment, load analysis, and code-compliant deployment across Canada. Contact us for a consultation: or call 438-881-3363.
Need more backup time than the numbers show? See our buyer's guide to extended runtime UPS and rackmount models.
Talk to a Canadian UPS specialist
Send us your equipment list and we'll spec the right UPS, including extended battery pack options if you need longer runtime than a single UPS can deliver.