The APC Smart-UPS family covers two fundamentally different power topologies under one brand. Standard Smart-UPS (SMT, SMC, SMX, SMTL) models are line-interactive. Smart-UPS RT and the newer Smart-UPS SRT are online double-conversion. They look similar, share a model-number convention, and are sold side by side — but they protect your equipment differently and are priced accordingly.
Quick comparison: Smart-UPS vs Smart-UPS RT/SRT
| Feature | Smart-UPS (SMT / SMC / SMX) | Smart-UPS RT / SRT |
|---|---|---|
| Topology | Line-interactive | Online double-conversion |
| Transfer time | 2–4 ms typical | Zero |
| Output regulation | ±8% via AVR | ±2%, fully regulated |
| Frequency conditioning | No — passes input frequency | Yes — regenerated output |
| Output waveform | Pure sine wave (on battery) | Pure sine wave (always) |
| Capacity range | 500 VA – 10 kVA single-phase | 1 kVA – 20 kVA single-phase, up to 200 kVA three-phase |
| Form factor | Tower, rack, rack/tower | Rack/tower convertible (SRT), tower (SURT) |
| External battery support | SMX series only | All models — extensive runtime via XLBP packs |
| Network management | Optional SmartSlot card (AP9640/41/43) | Often included; SmartSlot bay for upgrades |
| Best for | Workstations, network closets, small servers | Servers, medical, telecom, industrial, generator sites |
| Price multiplier | Baseline | 1.8x – 2.5x baseline |
What "Smart-UPS" means
"Smart-UPS" is APC's premium line-interactive product family — the step up from Back-UPS (entry-level standby) and below the dedicated three-phase Galaxy and Symmetra ranges. Standard Smart-UPS models share these traits:
- Line-interactive topology with auto-voltage regulation (AVR) that corrects sags and swells without using the battery
- Pure sine wave output on battery — important for modern equipment with active PFC power supplies
- SmartConnect remote monitoring (newer SMT/SMC units)
- Replaceable battery cartridges (RBC series) for hot-swap servicing
- Network manageable via the SmartSlot bay accepting AP9640, AP9641, or AP9643 cards
The sub-families — SMT, SMC, SMX, SMTL — distinguish form factor, lithium-ion vs lead-acid batteries, and external battery pack support. All are line-interactive.
Browse our APC Smart-UPS catalog for current SMT, SMC, and SMX inventory.
What "Smart-UPS RT" and "SRT" mean
The RT (Rack/Tower) and the newer SRT designation identify the online double-conversion members of the Smart-UPS family. These are physically larger, heavier, and run hotter than their line-interactive siblings because the inverter is always carrying the load. In return you get:
- Zero transfer time — the output never sees a switching transient
- Full output regulation regardless of input voltage or frequency
- Generator compatibility — handles frequency drift transparently
- Wider input voltage tolerance — typically ±20–30% before transferring to battery
- Galvanic-class isolation between input and output
SRT replaced SURT as the current generation in the late 2010s and is what APC ships today for new orders. Browse our APC Smart-UPS RT and SRT catalog.
Decoding APC model numbers
| Prefix | Topology | Form factor | Example |
|---|---|---|---|
| SMT | Line-interactive | Tower or rack | SMT1500, SMT1500RM2UC |
| SMC | Line-interactive (compact) | Tower | SMC1500, SMC1500-2UC |
| SMX | Line-interactive (extended runtime) | Rack/tower | SMX1500RM2UC, SMX2200RMLV2U |
| SMTL | Line-interactive (lithium-ion) | Tower | SMTL1500RM3UC |
| SURT / SURTA | Online double-conversion (legacy) | Rack/tower | SURTA1500XL, SURT3000XLT |
| SRT | Online double-conversion (current) | Rack/tower | SRT1500XLA, SRT5KRMXLT, SRT8KXLT |
How to choose between Smart-UPS and Smart-UPS RT
Choose Smart-UPS (SMT/SMC/SMX) when:
- Your utility power is reasonably stable
- You're protecting workstations, network gear, NAS, or 1–2 small servers
- The equipment downstream tolerates a few-millisecond transfer
- You want to maximize battery life and minimize energy cost
- You have a per-unit budget under roughly $1,000 CAD for a 1500 VA class unit
Choose Smart-UPS RT or SRT when:
- You're protecting servers, virtualization hosts, or storage arrays
- The site uses generator backup and clean handoffs matter
- Equipment includes medical devices, lab instruments, or industrial controls
- Utility power is unstable — frequent sags, surges, or frequency drift
- You need extended runtime via multiple external battery packs
- Zero transfer time is a hard requirement
Replacement battery cross-reference
Smart-UPS and Smart-UPS RT use different replacement battery cartridges (RBCs). A common mistake is ordering an RBC for the wrong topology — they are not interchangeable. Use our replacement battery catalog to match by exact UPS model, or contact us with your model number and we'll confirm the correct part.
Frequently asked questions
Is a Smart-UPS RT online or line-interactive?
Smart-UPS RT and SRT models are online double-conversion. They are the only members of the Smart-UPS family that use this topology. All other Smart-UPS sub-families — SMT, SMC, SMX, SMTL — are line-interactive.
What is the difference between SURT and SRT?
Both are online double-conversion. SURT (and SURTA) is the legacy generation; SRT is the current generation introduced in the late 2010s. SRT brings higher efficiency, a touchscreen LCD on larger models, longer warranties, and updated network management. SURT models remain field-supported and many are still in active service.
Why is the Smart-UPS RT so much more expensive?
Online double-conversion requires a continuously-running inverter, larger transformers, additional power electronics, and more substantial cooling than line-interactive. The hardware cost reflects that complexity. Most buyers see the premium recovered the first time the UPS prevents a corrupted database or a damaged power supply.
Can I replace a Smart-UPS with a Smart-UPS RT directly?
Electrically, yes — same outlet types and similar input requirements at most capacity points. Physically, RT/SRT units are heavier, deeper, and run warmer, so verify rack depth and ventilation before swapping. The RT will also draw more current at idle because the inverter is always running.
Do Smart-UPS RT models come with a network management card?
Most current SRT models ship with an AP9640 or AP9641 network management card pre-installed. Older SURT units typically required the card as a separate purchase. We confirm card inclusion on the product page for each unit we list.
Shop with confidence
UPSPLUSBATTERY has stocked APC Smart-UPS and Smart-UPS RT systems since 2012. Browse our full APC catalog, compare topologies in our line-interactive vs online guide, or use our UPS sizing guide to choose the right capacity. Questions on a specific model? Contact our team in Delson, Quebec — we ship across Canada.