Which fits your business better, dozens of small distributed UPS units or one central battery for servers, IT and production lines?

Centralized or distributed UPS? Small UPS units fit when only a few servers must shut down cleanly. When offices, IT and a production line must run through a real power cut, one central battery is usually better. Our guide to emergency power for your business compares the options, and our business battery systems cover the central route.

Count them: one under the reception desk, two in the server rack, one at every till, one per control cabinet. Each has its own battery, its own replacement date and its own idea of what to do when the power returns. Nobody has the full list.

What is the difference between distributed UPS units and one central battery?

Distributed means a small UPS next to each device or rack. Central means one system that feeds whole circuits from one place. That is a large UPS in a technical room, or a battery system whose inverter forms its own grid when the mains fails.

Small UPS units protect devices, not the business: the production line, cold room and lighting usually have no protection. Delta writes that distributed units cost less up front and grow step by step, but managing them "can, at times, burden" IT staff.

According to xpcc, a fault in one rack UPS "affects that rack, not the row, not the floor". A central unit concentrates that risk, so large sites build it redundant (N+1: one unit more than needed).

According to Vertiv, an offline UPS breaks for about 6 to 8 milliseconds, an online double-conversion UPS not at all. Victron states the Quattro takes over in under 20 milliseconds, fast enough for computers. For the devices themselves, read whether a business needs a solar inverter, a battery inverter or a UPS.

How long do UPS batteries last, and what does that mean for dozens of units?

Most small UPS units use lead-acid (VRLA) batteries that last three to five years, according to APC and Vertiv. A UPS itself runs seven to ten years, Vertiv adds, so UPS battery replacement comes once or twice.

Heat makes it worse. According to APC, every 8 °C above the ideal 20 to 25 °C halves battery life. The battery inside a UPS is always warmer than the room, so a unit under a desk or in a hot workshop ages fastest.

Thirty units on a four-year cycle means seven or eight new battery packs every year. Self-tests miss failing packs: one IT manager found a server room smelling of a cooked battery a day after its self-test. The pack was two months short of four years old.

On IT forums, other units were never replaced because nobody knew they were there. A central system has one bank: in our monitoring software you set a low-battery alert and follow consumption per phase.

As xpcc puts it, the battery is the heaviest and most maintenance-hungry part of any UPS architecture. Our article on service, warranty and maintenance for a business battery explains what to ask for.

Can one central battery replace the UPS units in your server room?

For most IT loads, yes: a battery inverter that takes over in less than 20 milliseconds keeps computers running. In our 3 x 400 V off-grid case, the UPS main output of each Quattro takes over the load in under 20 ms.

The exception is storage, core switches or a control PLC that must never see a gap: keep a small online UPS there. Put it behind the central battery: the small UPS covers the milliseconds, the central battery the hours. A few units then replace dozens, and their batteries are rarely used.

A cut under the Belgian load-shedding plan normally lasts a few hours; see what a blackout in Belgium means for a company. For a day or longer, a generator started by the battery system beats a very large battery: see generator and battery together.

What about backup power for production lines, PLCs and machines?

Production lines are where small UPS units fall short. A UPS in the control cabinet keeps the PLC alive, but motors, drives and compressors stop. Restarting a half-finished batch is often the most expensive part.

The AREI (the Belgian electrical safety code) names a production line, a server room and a control room as critical installations. The operator picks them through a risk analysis, lists per circuit how long it must work, and the inspection checks it. Then size on those circuits:

Cold rooms hold their cold a while, as how long a battery keeps a cold room cold in a power cut works out.

Can a UPS run for 4 hours?

A small UPS rarely can, and it is not built for it. One supplier guide calls five to fifteen minutes of UPS runtime enough in most cases: time for a clean shutdown or a generator start. Hours need a battery sized in kWh.

One IT manager on a forum got a day of notice for a three-hour cut, with 1 hour 40 minutes of UPS runtime. Another had clients whose units stayed off after a long night cut, until someone drove in.

With a central battery, the inverter takes over within 20 milliseconds and the solar panels keep producing on the island grid. At the lower limit a generator can take over, and when the grid returns the battery recharges by itself.

What does that look like on a real site? Below are three battery systems we installed, each running its site from one central system instead of many small boxes. Tap a project for the details.

Our media section also shows a Victron back-up system for an airport control tower, where hours matter.

Is a central battery more expensive than dozens of UPS units?

Up front, usually yes. Over ten years, the costs off the first invoice change the comparison.

• Battery replacements: one or two per unit, plus the time to find and swap them.
• Losses: an online UPS converts power twice, all day; a study cited by Consulting-Specifying Engineer gives about 90% efficiency at 30% load, 94% at full load.
• No return on normal days: a UPS waits, while a central battery can shave your peaks and store solar power.
• The cut itself: a stopped line, lost batch or spoiled stock easily costs more than the equipment.

In a Victron system you set a minimum state of charge in ESS; the manual states it is only used when the grid fails. Above it, the battery trims the quarter-hour peak behind your capacity tariff. Our explainer on calculating the capacity tariff for businesses shows what that is worth.

When do separate small UPS units remain the better choice?

When only a few devices matter, and minutes are enough. A small office with one server and a network cabinet does not need a central battery for continuity alone.