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NVR UPS Runtime Calculator

Estimate how long a UPS can keep your NVR, PoE cameras, PoE switch, router, and security camera system running during a power outage.

NVR, cameras, and UPS

Enter the backup battery and the devices that must stay online during an outage.

Battery input

Common sealed lead-acid UPS batteries are often 12 V.

Use amp-hours from the battery label.

For 2 x 12 V 9 Ah batteries, enter 2.

Use output watts if listed. VA rating alone does not tell runtime.

Common targets are 30, 60, or 120 minutes.

Target presets

UPS type

Common for NVR closets and small racks. Runtime still depends on battery Wh and load watts.

Battery condition

Assume the battery can deliver close to its rated capacity.

Include hard drives if the NVR spec separates them.

Use switch self-consumption, separate from camera PoE load.

Count cameras that must stay powered during the outage.

Use max watts with IR, heater, PTZ, or night mode if relevant.

Camera count presets

Camera watt presets

Set to 0 if network gear is on a different UPS.

Add monitor, alarm panel, gateway, or other required gear.

Reserve keeps the estimate conservative.

Estimated NVR UPS runtime

2 hr 1 min

165 Wh usable battery divided by 82 W total camera-system load gives about 2 hr 1 min of backup runtime.

Total system load
82 W
Usable battery
165 Wh
Target met
Yes
Recommended battery for target
107 Wh
UPS output load
14%

Runtime estimate

Based on usable Wh after UPS losses, battery age, and reserve.

2 hr 1 min
0 min1 hr4+ hr

Load breakdown

NVR
18 W
PoE switch base
12 W
Camera PoE load
42 W
Router / modem
10 W
Other load
0 W
Recommended output rating
103 W

Practical NVR backup: This should cover many short outages if the UPS is healthy and the load estimate is realistic. This is a practical estimate. Test the UPS under the real camera load before relying on it for security coverage.

Quick answer

With the default example, 165 Wh usable battery divided by 82 W total camera-system load gives about 2 hr 1 min of backup runtime.The load is 82 W, so a healthy UPS with 216 Wh of battery energy can meet a 60-minute target under these assumptions.

How to use this NVR UPS runtime calculator

Start with the UPS battery energy. If the UPS lists watt-hours, enter Wh directly. If it lists batteries such as 12 V 9 Ah x 2, use the battery-spec input so the calculator can convert voltage, amp-hours, and battery count into nominal Wh.

Then enter the devices that must stay online: the NVR, PoE switch self-consumption, camera PoE load, router or modem, and any other required equipment. For cameras, use maximum power draw if night IR, heaters, PTZ movement, or long cable runs can increase load.

If you are still choosing the switch, use the PoE Switch Power Budget Calculator first to check port count, per-port power, and total PoE budget. If the question is video retention instead of outage runtime, use the Security Camera Storage Calculator.

NVR UPS runtime formula

nominal battery Wh = battery voltage x battery Ah x battery count
usable Wh = nominal Wh x UPS efficiency x battery condition x (1 - reserve %)
total load W = NVR W + switch W + camera count x camera W + router W + extra W
runtime hours = usable Wh / total load W
recommended battery Wh = target hours x total load W / usable fraction

The calculation uses watt-hours for stored energy and watts for load. UPS VA rating and output watts are still important, but they do not directly predict runtime unless the stored battery energy is known or supplied by a vendor runtime chart.

Assumptions and methodology

This NVR UPS runtime calculator is intentionally conservative. It treats the UPS battery as nominal energy, then reduces it for conversion losses, battery condition, and reserve. The result is a planning estimate, not a guarantee for a specific UPS model.

  • Use actual device watts from labels, data sheets, or a power meter when possible.
  • Keep monitor, TV, desktop PC, and nonessential loads off the camera UPS unless the UPS is sized for them.
  • Use a larger reserve for old batteries, outdoor cameras with heaters, PTZ cameras, or security-critical installations.
  • For a final purchase, compare this estimate with the UPS vendor's runtime chart at a similar load.

Example calculations

6-camera NVR UPS runtime example

Suppose a small PoE camera system uses a 216 Wh UPS battery, one NVR, a PoE switch, six cameras, and a router. The total estimated load is 82 W.

After UPS efficiency, battery condition, and reserve, usable battery energy is 165 Wh. Dividing that by the load gives about 2 hr 1 min of runtime.

If the same UPS also powers a monitor or more cameras, the total watts increase and runtime drops. If the goal is a full two hours, the calculator shows the recommended battery Wh needed for that target.

NVR UPS runtime chart

These examples use a healthy line-interactive UPS, 10% reserve, and common planning loads. Replace the values with your actual UPS and camera system before buying equipment.

NVR UPS runtime examples
SetupLoadBatteryUsableRuntimePlanning note
4-camera home NVR55 W108 Wh82.6 Wh1 hr 30 minPractical NVR backup
6-camera PoE kit82 W216 Wh165 Wh2 hr 1 minPractical NVR backup
8-camera small office118 W300 Wh230 Wh1 hr 57 minPractical NVR backup
12-camera higher-power system189 W512 Wh392 Wh2 hr 4 minPractical NVR backup

Choosing a backup target

A 15-30 minute target is mainly for brief power interruptions. A 60-minute target is a practical home NVR UPS starting point. A 2-4 hour target is more appropriate when the camera system must keep recording through longer outages or when the property is not attended.

If remote alerts matter, include router, modem, ONT, or gateway power in the same runtime plan. For a network-only estimate, the Router Backup Power Runtime Calculator gives a smaller dedicated calculation.

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FAQ

How do I calculate UPS runtime for an NVR?
Estimate the total watts for the NVR, PoE switch, PoE cameras, router or modem, and any other required devices. Then divide usable battery watt-hours by that total load. Usable watt-hours should account for UPS efficiency, battery age, and reserve.
Does UPS VA rating tell me NVR runtime?
No. VA or output watts tells you how much load the UPS can support, but runtime depends on stored battery energy in Wh, the actual camera-system load in W, UPS losses, battery condition, and reserve.
Should camera watts be included if the cameras use PoE?
Yes. If the UPS powers the PoE switch, the camera PoE load still comes from the UPS through the switch. Include switch self-consumption and camera watts separately so the load estimate is not understated.
How much UPS runtime is enough for a security camera system?
For a home system, 30-60 minutes may be enough to cover short outages. For a small business, gate, or remote property, 2-4 hours may be more practical. The right target depends on how long recording must continue when utility power is down.
Why is real NVR UPS runtime shorter than the estimate?
Real runtime can be shorter because batteries age, UPS efficiency varies by load, infrared night mode increases camera power, PTZ motors or heaters draw more power, and some UPS models shut down earlier under low-battery conditions.
Should I keep the router on the same UPS as the NVR?
If remote viewing, alerts, or cloud recording matter during an outage, include the router, modem, ONT, or gateway load. If you only need local recording, those devices can be on a separate UPS or excluded from this estimate.
Can I plug a monitor into the NVR UPS?
Only if the UPS is sized for it. A monitor can use as much or more power than the NVR itself and can sharply reduce runtime. For backup recording, keep only essential devices on the UPS.