{"id":2797,"date":"2026-10-11T16:01:32","date_gmt":"2026-10-11T13:01:32","guid":{"rendered":"https:\/\/systemtech.fi\/?post_type=stg_guide&p=2797"},"modified":"2026-10-16T16:41:42","modified_gmt":"2026-10-16T13:41:42","slug":"ups-valinta-ja-mitoitus","status":"publish","type":"stg_guide","link":"https:\/\/systemtech.fi\/en\/oppaat\/ups-valinta-ja-mitoitus\/","title":{"rendered":"Choosing and sizing a UPS"},"content":{"rendered":"\n
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SYSTEMTECH \/ UPS AND BACKUP POWER<\/p>

Choosing and sizing a UPS<\/h1>

Choose a UPS in three steps: sufficient watt and VA capacity, the required runtime, and shutdown support for your equipment. The VA rating alone does not determine the right choice.<\/p>

Selection guide<\/span>16.10.2026<\/span><\/div><\/div>\n
01<\/span>ST \/ TECH<\/strong>NETWORK \u00b7 POWER \u00b7 SYSTEMS<\/em><\/div><\/div>\n <\/header>\n \n\n\n
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1. Calculate the actual UPS load<\/h2>

List the router, switch, NAS, NVR and other devices connected to battery-backed outlets. Measure the mains-side AC load while disks start and camera night lights are on. If you measure the entire AC load of a PoE switch, its cameras and APs are already included. Do not add them a second time.<\/p>

A power supply’s rated output is its capacity, not the device’s usual consumption. If measurement is unavailable, use a justified manufacturer maximum and record the uncertainty.<\/p>

2. Example of watt and VA sizing<\/h2>

Assume a 180 W load and a measured or justified estimated load power factor of PF 0.9. Apparent power is 180 \/ 0.9 = 200 VA. Adding 25 % growth allowance gives minimum capacities of 225 W and 250 VA. Both limits must be met; this does not yet establish 15 minutes of battery runtime.<\/p>

The load’s PF is not the ratio of the UPS’s rated watts to VA. If PF is unknown, measure it with a suitable meter or confirm the connected equipment’s specifications.<\/p>

3. Select runtime separately<\/h2>

Use the chosen UPS manufacturer’s runtime curve at the actual 180 W load. A 25 % capacity margin does not increase runtime by 25 %. If the future load grows, check runtime at that load too. Battery age, temperature and condition affect actual results.<\/p>

Example target: the NAS needs 4 minutes for a controlled shutdown, and you want to wait through a 3-minute outage before starting shutdown. Also allow the safety margin specified by the manufacturer; do not schedule shutdown for the estimated moment the battery runs out.<\/p>

4. UPS type and connections<\/h2>
Requirement<\/th>Selection criterion<\/th><\/tr><\/thead>
Network equipment and a small NAS<\/td>Compare a line-interactive model, its output waveform and compatibility with the equipment’s power supplies.<\/td><\/tr>
Sensitive loads or strict continuity requirements<\/td>Compare an online double-conversion model, efficiency, noise and bypass arrangements against the site’s requirements.<\/td><\/tr>
NAS or server<\/td>USB, network or SNMP shutdown supported by the exact UPS, NAS and software versions.<\/td><\/tr>
Long runtime<\/td>A manufacturer-documented battery arrangement and any additional battery modules, rather than only a higher VA rating.<\/td><\/tr><\/tbody><\/table>

Count battery-backed Schuko\/IEC outlets separately from surge-only outlets. Check the supplied data and installation cables, battery replacement, space and ventilation.<\/p>

5. Use the calculator and verify the installation<\/h2>

Enter the load, PF, growth allowance and runtime target in the calculator. Transfer the same values to the product selector. If no result is found, adjust only a real requirement or request site-specific sizing; do not reduce values merely to make a product appear.<\/p>

  1. Verify backups and test the shutdown connection according to the manufacturer’s instructions during a maintenance window.<\/li>
  2. Confirm that the NAS shuts down before battery exhaustion and that any network path needed for shutdown remains operational.<\/li>
  3. Test restoration of mains power and service startup. Record the load, battery age and shutdown times.<\/li><\/ol>

    Eaton: UPS sizing guide<\/a>; Synology: UPS compatibility<\/a>.<\/p>

    Continue with a practical implementation: NAS and UPS: controlled shutdown and a restorable backup<\/a>.<\/p>\n<\/div>\n\n\n

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    SIZING TOOL \/ UPS<\/p>

    Calculate the required UPS power<\/h2>

    Enter the devices' combined actual power consumption. The calculator accounts for growth allowance and load power factor.<\/p><\/div>\n

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