Single-phase online UPS
Online rack and tower UPS
Online double-conversion UPS with lead-acid batteries, for server rooms, network cores and critical equipment. The P91 converts between rack and tower; the T91 is a tower. Both regenerate the output continuously, so the load never sees a transfer.
Compare models
Rack or tower, 1-3 kVA
Converts between rack and tower mounting. Unity power factor; external battery packs extend runtime.
Tower
Stands beside the equipment it protects.
5-10 kW
Higher capacity in a rack, at 208V or 240/120V.
Want the same protection with lithium batteries? The P91 Li and J90 last up to 15 years. See lithium UPS →
How to choose
| If you need | Start with |
|---|---|
| Online protection in a 19-inch rack, 120V | P91 |
| The same at 208/230V | P91g |
| A tower beside the equipment | T91 or T91i |
| 5-10 kW at 208V or 240/120V | P91 5-10k |
| Lithium batteries instead of lead acid | P91 Li or J90 |
| N+1 redundancy or room to grow | M90S modular UPS |
Frequently asked questions
What is an online double-conversion UPS?
It converts incoming AC to DC and back to clean AC continuously, so the load always runs from the inverter. When the utility fails there is no transfer, because the load was never on utility power.
Can I add runtime?
Yes. External battery packs extend runtime on the P91 family. Our engineers can size the packs to the runtime you need at your load.
Rack or tower?
The P91 converts between the two, so one model covers a 19-inch rack or a floor installation. The T91 is a tower only.
What does unity power factor mean?
The UPS delivers its full rating in watts as well as volt-amperes, so a 3 kVA unit can support a 3 kW load. Many UPS are rated at 0.8 or 0.9, which gives less real power for the same kVA.
Are these UPS TAA compliant?
Yes, the P91 and T91 families are. See the TAA-compliant single-phase UPS page for details.