Online UPS units are double-conversion uninterruptible power supplies for servers, network equipment, medical and lab devices and other sensitive electronics. Our range covers tower, rackmount and convertible rackmount/tower models from 1 kVA to 6 kVA, with brands including APC, CyberPower, Eaton and Qoltec.
How to choose an online UPS
Capacity. Add up the power draw of everything you plan to connect, then leave 20 to 30 per cent spare. Online UPS units are rated in kVA, but the usable wattage is lower and depends on the power factor, so check the watt rating in the specification. Our range includes 1, 1.5, 2, 2.2, 3 and 6 kVA models, and 3 kVA is well represented.
Form factor. Tower models stand on the floor or under a desk, while rackmount models fit a 19-inch cabinet. Convertible rackmount/tower units can be used either way, which helps if you may move equipment into a rack later. For rack units, measure the cabinet depth before ordering.
Outlets. C13 outlets take standard IEC leads from servers, switches and storage, and C19 outlets suit higher-draw equipment. Type F outlets accept ordinary mains plugs, and some models have a terminal block for hardwired connections. Match the outlet types to your devices so you do not need many adapter leads.
Input and output voltage. A wide input voltage and frequency window lets the UPS cope with unstable mains or a generator without switching to battery. Some models in our range accept input up to 300 V and a frequency window of 40 to 70 Hz. Check the nominal output voltage too: our range lists 200, 208, 220 and 230 V, and your equipment should be rated for the one you choose.
Battery runtime. Runtime depends on the load and the battery capacity, not only on the kVA rating. If you need longer backup, check whether the model accepts external battery packs, and plan to replace the internal batteries every few years.
Online UPS brands we carry
- APC: a Schneider Electric brand, known for the Smart-UPS family used in server rooms and small offices.
- CyberPower: a Taiwanese manufacturer that makes UPS units alongside power distribution units for racks.
- Eaton: a power management company whose 9SX and 9PX series are established online UPS lines for IT rooms.
- Vertiv: the company behind the Liebert UPS brand, focused on data centre power and cooling.
- FSP Group: originally a maker of PC power supplies, which it has extended into UPS products.
- Power Walker: sold by BlueWalker, known for its VFI range, the designation for double-conversion online models.
Also in our range: Qoltec, Conceptronic, Online USV, Green Cell, Ever and LevelOne.
Online UPS FAQ
What is an online UPS?
An online UPS is a power supply that constantly converts incoming mains power to DC and back to clean AC for your equipment. Because the connected devices always run from this inverter, there is no switchover delay when the power fails. It also filters out voltage spikes, sags and frequency variations.
What is the difference between an online and a line-interactive UPS?
A line-interactive UPS passes mains power through and only switches to battery when there is a problem, which causes a very short transfer time. An online UPS feeds the load from its inverter at all times, so it offers the most stable output. Online models usually cost more and use more energy, so they suit servers and critical equipment rather than casual use.
What size online UPS do I need?
Add up the wattage of all connected devices and choose a UPS whose watt rating exceeds that total by at least 20 to 30 per cent. Check the watt figure, not just the kVA, as the two differ. A single server and switch may need only 1 kVA, while a small rack of equipment is more likely to need 3 kVA or more.
Can I use an online UPS with a generator?
Yes, many online UPS units work well with generators because they condition the incoming power. A wider input voltage and frequency window makes this easier, since generator output can vary. Check the input specification and the generator rating, and size the generator above the UPS load.
