Online UPS Buying Guide (India): When You Need One, How to Size It & Price
Double-conversion UPS, explained plainly: when you really need one, how big, how long it runs, and what it costs.
Quick answer
An online (double-conversion) UPS rebuilds the mains into clean, regulated power with zero transfer time, so servers, CCTV racks, billing systems and medical equipment never see a glitch. Total your critical load in watts, add 20–25% headroom, and add an external battery bank if you need more than the few minutes the internal batteries give.
What an online UPS actually is
In an online UPS the incoming mains is converted to DC and then rebuilt back into a fresh, regulated sine wave — continuously, even when grid power is fine. Your equipment always runs off that rebuilt output, completely isolated from spikes, sags, brownouts and frequency drift. Because the inverter is always carrying the load, there is no transfer time when the grid fails: the battery simply keeps the same output going. That is the key difference from a home inverter (a 10–20 ms gap) and from a line-interactive UPS (a few milliseconds).
The essentials
- Double conversion: the load always runs off a freshly rebuilt sine wave, isolated from the mains.
- Transfer time is zero — versus ~10–20 ms for an inverter and a few ms for a line-interactive UPS.
- Internal batteries give a few minutes (safe shutdown or bridge to a generator); for hours you add an external battery bank.
- Most online UPS are rated at 0.8 power factor — a 1 kVA unit carries about 800 W; some lithium models (MAX LiFe) are unity (kVA = kW).
- Microtek single-phase ranges: E² (1 kVA), MAX+ (1–10 kVA), iMAXX (5.5–10 kVA), MAX LiFe lithium (3–5 kVA).
Do you actually need an online UPS?
Be honest about the load, because online UPS is the most expensive option and most homes and small offices do not need it. You need online-grade protection when even a momentary disturbance causes data loss or damage — a server or NAS, a network and storage rack, a CCTV/NVR system you cannot afford to lose footage from, a POS or billing server, or sensitive medical and lab instruments. For an ordinary desktop, router or billing counter, a line-interactive UPS is plenty; for household backup you want an inverter.
| Home inverter | Line-interactive UPS | Online UPS | |
|---|---|---|---|
| Transfer time | ~10–20 ms | A few ms | Zero |
| Output | Pure/quasi sine | Mains with AVR | Continuously rebuilt, fully clean |
| Best for | Lights, fans, fridge, home backup | PC, router, billing counter, DVR | Servers, network/CCTV racks, medical/lab, POS server |
| Microtek range | LUXE / Elite | UPS LEGEND | E² / MAX+ / iMAXX / MAX LiFe |
Inverter vs line-interactive UPS vs online UPS
How big — sizing in one paragraph
Total the watts of everything that must stay on, then size to the UPS's watt (kW) rating — not just its kVA — and leave 20–25% headroom for safety and future additions. Because most online UPS are 0.8 power factor, a 1 kVA / 800 W unit comfortably carries about 600–650 W of real load; step up if you are close to the limit. Our full sizing guide walks through it with worked examples for a server, CCTV and a clinic.
VA ↔ Watts Converter
InteractiveInverters and UPS are sold in VA, but your appliances are rated in watts. Here's the bridge.
Real power
800 W
Usable wattage you can run.
Rule of thumb
VA × 0.8 ≈ Watts
Keep ~20-30% headroom on top for surge and low mains voltage.
Power factor (PF) is how 'in step' current and voltage are. Indian home inverters are usually quoted at PF 0.8, so a 1000 VA inverter delivers about 800 W. Motors and pumps have a lower PF (more startup surge); pure resistive loads like bulbs are near 1.0.
Convert your load between watts and VA to read it against a UPS rating
How long it runs: internal batteries vs an external bank
An online UPS ships with internal batteries sized for ride-through — typically a few minutes at load, enough to save work and shut down cleanly, or to bridge the gap while a generator starts. If you need real runtime — an hour of CCTV, or a clinic counter that rides out a long cut — you add an external VRLA battery bank sized to your target, wired to the UPS's DC bus (24V on a 1 kVA up to 192V on a 10 kVA). We size, supply and install that bank across Delhi NCR.
Single-phase or three-phase?
Almost every shop, clinic, office and small server room runs on a single-phase supply, and Microtek's single-phase online range covers 1 kVA right up to 10 kVA — which is enough for the vast majority of these loads. You only move to a three-phase UPS for genuinely large or three-phase installations. If you are not sure what your premises has, tell us your meter and load and we will confirm.
What it costs
As a rough guide, single-phase online UPS runs from about ₹16,000 for a 1 kVA up to roughly ₹1,15,000 for a 10 kVA, before any external battery bank. Capacity, single vs three phase, whether batteries are built in, and lithium vs sealed VRLA all move the figure. Our online UPS price guide breaks it down by capacity, and the live category page shows current prices.
Where to next
Frequently Asked Questions
What is the difference between an online UPS and an inverter?
An online UPS continuously rebuilds the output and switches over with zero gap, giving perfectly clean power for servers and sensitive electronics. A home inverter has a 10–20 millisecond changeover and is built for household backup of lights, fans and a fridge, not critical loads.
Do I need an online UPS or a line-interactive one?
If the load is a single PC, router, billing counter or CCTV DVR, a line-interactive UPS (Microtek LEGEND) is enough and far cheaper. Choose online only for servers, network/storage racks, POS servers and medical or lab gear where any glitch means data loss or damage.
How long does an online UPS run during a power cut?
On its internal batteries, usually a few minutes — enough for a safe shutdown or to start a generator. For longer runtime you pair it with an external battery bank sized to the hours you need, which we configure and install across Delhi NCR.
Need help choosing?
Share your requirement and our team will recommend the right product and size for your home or business. Genuine stock, home installation, old-battery exchange, and on-site service & AMC across Delhi NCR — in business since 1998.