Online UPS units are uninterruptible power supplies with double conversion, used to protect servers, network equipment and other sensitive hardware. The category covers over 130 models in tower, rackmount and convertible rackmount/tower form. Brands include BlueWalker, APC, Online USV-Systeme, Eaton and CyberPower.
How to choose an online UPS
Power rating. Add up the consumption of everything you plan to connect in watts and leave 20-30% headroom. kVA and watts are not the same thing, because the power factor decides the real output, so check the wattage rating. Our range runs from 1 to 6 kVA, mostly 1, 2 and 3 kVA.
Runtime. Battery capacity decides how many minutes your equipment keeps running when the mains fails. Standard models are generally meant to give you time to shut systems down safely, and longer runtimes usually need extra battery modules.
Form factor. A tower UPS stands on the floor or under a desk, while a rackmount unit fits a 19-inch cabinet. Our range includes tower and rackmount models, convertible rackmount/tower units that can be used either way, and a few desktop units.
Output sockets. C13 sockets suit computers, switches and many servers, while C19 sockets are for higher-power equipment. If you connect devices with ordinary plugs, choose a model with Type F (Schuko) outlets. Check that there are enough sockets for every device.
Input tolerance. The wider the input frequency and voltage window, the less often the UPS has to fall back on its battery because of unstable mains. Our range includes models with an input frequency of 40-70 Hz and a maximum input voltage of up to 300 V. This also helps when running from a generator.
Brands we carry
- BlueWalker and PowerWalker: the German company BlueWalker sells its UPS units under the PowerWalker name.
- APC: a Schneider Electric brand, known for its Smart-UPS and Back-UPS lines.
- Online USV-Systeme: a German manufacturer that specialises in uninterruptible power.
- Eaton: a power management company whose UPS units are widely used in server rooms and data centres.
- CyberPower: a Taiwanese manufacturer offering both tower and rackmount UPS units.
- Vertiv: a data centre infrastructure company, formerly Emerson Network Power, known for Liebert UPS systems.
Also in our range: Conceptronic, Qoltec, Digitus, LevelOne and FSP Group.
Online UPS: frequently asked questions
What is the difference between an online and a line-interactive UPS?
An online UPS powers your equipment continuously through an inverter (AC-DC-AC), so the load is isolated from the mains and there is no break when it switches to battery. Line-interactive models usually feed equipment straight from the mains and switch over when the voltage falters, with a very short gap. Online units cost more, but they are meant for servers and other equipment that needs clean, stable power.
What size UPS do I need for a server?
Add up the power draw of all connected devices in watts, add 20-30% headroom and choose a UPS whose wattage rating exceeds that total. A single small server with network gear often needs 1-2 kVA, while a cabinet with several servers needs 3 kVA or more. Always look at watts, not only kVA.
How long does an online UPS run without mains power?
It depends on the battery capacity and the load. At full load a standard model typically runs for a few minutes, and at a light load for longer. External battery modules are used to extend the runtime.
Can an online UPS be connected to a generator?
Usually yes, especially if the UPS tolerates a wide input voltage and frequency range. The generator's capacity should be well above the UPS rating, and it is worth checking the manufacturer's recommendations first. Without that margin, an unstable generator output can make the UPS keep switching to battery.
