Understand your UPSs’ total cost of ownership

Understand your UPSs’ total cost of ownership

By Jack Ward, MD of Powermode

Thanks to South Africa’s frequent, often unexplained, power outages and disruptions, uninterruptible power supply (UPS) systems play a vital role in terms of keeping the wheels of business turning. Unplanned downtime can be costly. In fact, most organisations’ reputation and very survival depend on the availability of their electrical power supplies. This places the emphasis on quality purchases for these essential standby systems.

In this light, when budgeting for a UPS system, it’s crucial to consider the total cost of ownership (TCO) - rather than just the original purchase price. When operating costs and upgrades are taken into account, a unit with an apparently cheaper initial purchase price can often prove to be more expensive in the long run than a better-technology solution at a slightly higher original price point.

In reality, a UPS featuring modern, modular technology can reduce the TCO significantly, while improving reliability and dependability.

To secure first class UPS protection, business managers should accept that the best-performing UPS technology - as found in the latest modular systems - will cost a little more, but within a year the cost difference could well be recovered in its entirety.

Before explaining how this is possible, let me highlight the evolutionary path along which UPS technology has travelled, generating cost-saving benefits to complement improved technical performances along the way.

Legacy UPS systems, featuring transformers, were large and heavy when compared to today’s systems. For example, a data centre with a 120 kVA load could theoretically have been supplied by a single, cumbersome, floor-standing 120 kVA unit. However, because fail-safe redundancy is a likely requirement to ensure availability, this would demand the fitment of two 120 kVA units sharing the load in a 1+1 redundant configuration.

For the organisation that the two UPSs’ served, it meant investing in substantially more capacity than actually necessary. It also meant that neither UPS unit could ever be more than 50% loaded, which for a transformer-based system results in a significant reduction in efficiency.

With the advent of transformerless technology has come much smaller and lighter UPS solutions which can easily be incrementally added to a racking frame to achieve an application’s required power capacity and redundancy targets. Unwieldy, free-standing individual units are now the dinosaurs of the standby power world.

In our hypothetical scenario, the 120 kVA load can now be met by a single rack containing four, 40 kVA ‘hot swap’ plug-in modules. The load remains fully supported with n+1 redundancy, while the total UPS capacity has been reduced from 240 kVA to 160 kVA.

Although the purchase price per kVA for modular UPSs will be slightly higher than for legacy types, this difference will be partly offset by the reduction in purchased capacity - and in the floor space required for installation.

Moreover, significant savings in operating costs will also be made as the modular solution is more efficient than a transformerless implementation – especially one that cannot operate at more than 50% loading. Considering the 120kVA example as discussed, over a five-year period, savings could be as high as R 500,000.

And that’s not the end of the story. A modern modular UPS systems’ can slash operating costs even further by reducing the need to hold emergency spare parts. Instead of a slew of costly spares that might be needed, a single spare plug-in module will suffice.

This is true even when modules of different power ratings are being used, because simply holding a module of the highest kVA rating installed will cover all eventualities. A trained technician can hot swap a UPS module in under 15 minutes. Repairing by module-swapping in this way can save up to 50% on logistics and stock management costs.

Modular system upgrading is also far simpler, faster and cheaper as extra capacity can be added simply by plugging in additional modules without even interrupting power to the critical load. The lengthy building work, sizable increase in footprint and frustrating interruption to supply associated with extending traditional systems is completely eliminated.

One final point: A UPS system’s availability is increased if its mean time to repair (MTTR) is reduced. An attractive feature of a modular UPS system is its zero MTTR figure. If a hot-swappable module does fail, it can be withdrawn from the UPS frame without interrupting power to the load. A replacement module can be plugged into the rack immediately.

By contrast, if a legacy system fails, it must be shut down, isolated from its mains supply and repaired in situ; a process that typically takes five or six hours to complete. This means that, unlike a legacy transformer-based system, a modular UPS solution can provide ‘six-nines’ (99.9999%) availability which equates to just 32 seconds of downtime per year.

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