Three general categories of scalable UPS units are:

Scalable, Redundant UPS units:

These are units that have power modules that are added to a UPS frame as the load increases. Typical power module sizes are: 3, 4, 5, 10, 12, 15, 25, 50, or 275 Kw. It is important to note that the batteries associated with these units must also be scalable or sized with the maximum load in mind. These units are intended to be used in an N+1 configuration to maintain a redundant power module.

Examples of scalable, redundant UPS from different manufacturers would be:

  • APC’s LX, PX100 or PX250/500
  • Emerson’s APS, or APM
  • Eaton’s 9170. BladeUPS, or 9395

Example: The APC PX has the ability to have 10 x 10 kW power modules running simultaneously. You would not run this unit above 90 kW so if one power module fails you can still support the load.

Soft Scalable UPS Units:

Soft scalable UPS units have a range of load that they can support. To upgrade, or scale them, you do not have to add any power modules. They are already constructed to handle the largest load in their frame size but require a field upgrade of their firmware by a factory service engineer to make them function. There is no redundancy built into this solution.

Examples of soft scalable UPS from different manufacturers would be:

  • Schneider/MGE Scalable: Galaxy 5000 40-50 kVA; 60-80 kVA; 100-130 kVA
  • Emerson’s NX 40, 60, 80kVA or NX 80, 100, 120, or 120, 160kVA
  • Eaton’s 9390 UPS is available from 20-160 kVA in 4 frame sizes: 40, 80, 120 & 160

Paralleling Switchgear:

Some UPS units can be paralleled (their outputs combined on one output bus). This can provide additional capacity, redundancy, or both. You could use the units listed above in this scenario or, more likely, utilize a less expensive fixed capacity UPS units. For example, you install a paralleling cabinet that will support up to four 80 kVA UPS units. Initially you install two units so that you have 80 kVA N+1, or 160 kVA. In the future, by adding additional units, you can grow to 240 kVA N+1 or 320 kVA.


In each of these cases it is advisable to install your input circuits sized to the maximum that the scalable solution allows so you don’t have to experience any downtime while upgrading.

Not all UPS units can be paralleled together even within the same manufacturer’s group of products.