UPS Runtime Calculator 2026 — How Long Will My UPS Last?

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UPS Runtime Calculator 2026 — How Long Will My UPS Last?

Calculate exactly how long your UPS battery will power your equipment during an outage. Supports multi-battery configs, battery aging factors, and a built-in equipment load builder for servers, NVR, network gear and more. Free, no signup.

UPS types

Max target runtime

VA↔W

Reverse sizing

Free

No registration

Will your UPS actually hold long enough when power goes out?

Most UPS runtime surprises happen during real outages — not during testing. Manufacturer specs are measured with new batteries at 25°C under ideal lab conditions. After 2–3 years, a lead-acid battery has already lost 20–30% of its capacity, and a hot equipment room can cut that further.

This calculator accounts for battery aging, UPS type (standby / line-interactive / online double-conversion), depth of discharge, conversion efficiency, and actual connected load — giving you a realistic runtime estimate rather than the optimistic number on the box.

The reverse sizing mode works the other way: enter your load and desired runtime to get the minimum UPS VA rating you need to buy. The equipment load builder includes presets for NVR, PoE switches, servers, workstations, routers, and more.

⚠️ Never load a UPS above 80% of its rated watt capacity. Runtime estimates assume stable resistive load — motors and drives draw surge current on startup.

What this tool calculates

✓Runtime at current load (minutes)

✓Runtime at 25%, 50%, 75%, 100% load

✓Battery aging and health impact

✓Multi-battery (series / parallel / both)

✓VA vs Watts conversion (PF calculator)

✓Reverse sizing — find the right UPS VA

✓Equipment load builder (NVR, switch, server)

✓Runtime vs load curve chart + print report

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Key concepts explained

VA vs Watts

Always compare Watts

A 1500VA UPS with 0.8 PF delivers 1200W. Always compare your load in Watts against the UPS watt rating — never VA alone.

Battery Aging

20–30% loss after 2 yrs

VRLA/AGM batteries last 3–5 years. Every 10°C above 25°C halves battery life. Replace proactively at 3 years for critical systems.

UPS Types

Online = best protection

Standby UPS has 4–12ms transfer time. Line-interactive handles sags/surges. Online double-conversion has zero transfer time — essential for servers.

NVR Load

120–280W typical

16-camera NVR + PoE switch = 120–280W total. A 1000–1500VA UPS provides 15–30 minutes — enough for graceful shutdown or generator start.

Common questions

▶ Why does my UPS runtime differ from the spec sheet?

Manufacturer runtimes are with new batteries at 25°C under ideal conditions. Real-world runtimes are shorter due to battery aging (20–30% capacity loss after 2–3 years), temperature above 25°C, startup surges from motors and drives, and UPS conversion losses. Set the health factor accurately in this calculator for realistic results.

▶ What is the difference between VA and Watts?

VA is apparent power (voltage × current). Watts is real power actually consumed. The ratio is the power factor (PF). A 1500VA UPS with 0.8 PF delivers 1200W. Always compare your equipment load in Watts against the UPS watt rating — many cheaper units only show VA, hiding a low power factor.

▶ When should I replace my UPS battery?

Replace when the UPS self-test fails repeatedly, runtime drops below 50% of original, the battery is swollen or leaking, or the UPS is over 4 years old. For critical systems (servers, NVR, medical), replace proactively at 3 years regardless of apparent condition. Li-ion UPS batteries last 8–10 years.

▶ Can I add external battery packs to extend runtime?

Yes — many mid-range and enterprise UPS units support external battery modules (EBMs) that connect directly and appear as additional capacity. Always use the same battery type and voltage, and ensure the UPS charger can handle the increased Ah capacity. Common for NVR systems and network closets requiring 30+ minutes of runtime.

▶ What UPS size for a CCTV / NVR system?

A 16-camera NVR (30–80W) + PoE switch (50–200W) + router (15–30W) = 120–280W total. Budget 15–25W per PoE camera at the switch level. A 1000–1500VA UPS gives 15–30 minutes on this load — enough for graceful shutdown or generator transfer. Use the equipment builder above to get an exact figure for your setup.