Selecting the Right Uninterruptible Power Supply to Protect Diagnostic Equipment

It happens thousands of times each day at hospitals and health care facilities around the country. Doctors need to take a look inside a patient, so they order a MRI, CT scan or X-ray. These fairly routine procedures only a take a few minutes to complete but can impact the facility’s finances and public reputation for years to come if they cause an unexpected electrical interruption. According to research from MeriTalk, an online government and health care IT community, 40 percent of global health organizations have experienced an unplanned outage in the last 12 months. The average cost is $432,000 per incident, and diagnostic imaging systems are among the leading culprits.

MRI, CT and X-ray machines have dynamic power demands, which create unique requirements for the critical power protection equipment supporting them. When idle, these imaging devices do not use a lot of power (usually between 5 and 20 kVA), but while scanning, the maximum power demand can reach up to 200 kVA for 10 to 50 milliseconds. These abrupt spikes in current may cause a power outage or damage the equipment if not properly managed, resulting in repeated diagnostic tests, wasted medical supplies, expensive repair calls and risks to patient safety.

To prevent electrical interruption, most hospitals and health care facilities install an uninterruptible power supply (UPS). UPS systems not only supply short-term power protection by bridging the gap between utility failure and generator start-up during an outage, but also condition incoming utility power, which is of equal importance to health care facility managers. These units regulate voltage when imaging equipment is in use, ensuring scans are successful and the facility does not lose power.

Traditionally, hospitals have relied upon UPS systems with valve-regulated lead acid batteries (VRLA) to backup diagnostic imaging systems and other critical applications, but these units come with a host of disadvantages, including exposure to hazardous gases and toxic contents. In recent years, UPS systems with integrated flywheel energy storage have disrupted the health and safety market and are actively reducing the health care industry’s dependence on VRLA batteries, but widespread adoption has been slow due to the risk-averse nature of hospital administrators.

Selecting the right UPS system for your facility is paramount, especially with patients’ lives on the line. Each hospital’s critical power requirements are unique, so there is not a one-size-fits-all solution, but here are four main factors to consider when selecting a UPS.

Total Cost of Ownership (TCO)

Battery-based UPS systems have long been the industry standard, not only because they can produce high amounts of current on short notice and have longer runtimes compared to other technologies available, but also because they have a relatively low initial cost. However, the operating expenses of these units can be quite high.

In order to function properly, batteries need to be kept at an ambient temperature of 77 degrees Fahrenheit, so they must be housed in special air-conditioned and well-ventilated rooms. Additionally, batteries must be maintained quarterly and replaced every four to eight years. While this preventative maintenance ensures the batteries are working, human error is the leading cause of site failures.

A number of factors go into calculating TCO for a UPS product, including initial cost and installation, energy losses based on product efficiency and cooling requirements, service and maintenance costs, and battery replacement costs. For facilities where budget constraints exist, flywheel-based UPS may be the better choice due to their high-energy efficiency, reduced cooling needs and permanent energy storage, which doesn’t require replacement every few years.

System Performance

Like all products, there is no point in purchasing something if it does not meet the demands of your facility’s applications. As mentioned above, health care facilities need a UPS system that can handle step loads when diagnostic imaging equipment is in use. Product specification sheets from vendors may only cover the system’s performance in standard operating modes, so be sure to research the UPS’s ability to handle overloads and step loads without going to bypass. Ask industry peers about the UPS products they use. Put simply, does the UPS work when called upon or do you run the risk of dropping a critical load due to the product’s inability to manage large swings in voltage?


The code requirements in the National Fire Protection Association (NFPA) standards and the National Electrical Code (NEC) require emergency power to be restored within 10 seconds in a hospital or similar facility in the event of an outage. On-site backup generators can keep a facility operational for as long as they have fuel, but can take up to 15 seconds to start and assume the load. Historically, several minutes of UPS runtime was preferred, but with the recent advancements in backup generator technology, longer ride-through time is no longer needed or advisable for cost-conscious end users.


When called upon, a UPS system is expected to work — no questions asked. For electrical equipment, reliability is measured by how likely a product is to fail. Although a fraction of a percentage may not seem like much, it is a big gamble when patients’ lives are at stake. When considering a UPS, ask for independent, third-party reliability assessments comparing their product with competitors.

When selecting a UPS, it’s important to consider all of these factors to ensure that you are purchasing and installing a system that meets your facility needs today and in the future. Take your questions about your facility needs and speak with others, including UPS manufacturers, health care facility engineers and consultants. Don’t be afraid to ask a vendor for customer referrals from facilities with similar requirements. Review relevant case studies. Request the supplier walk you through their TCO calculations. Only then will you have the information needed to make the right purchasing decision, so your doctors can order MRI, CT and X-rays of their patients without you having to worry if it will cause the lights to go out — or worse.

Todd Kiehn is the vice president of marketing and modular solutions for Austin, Texas-headquartered Active Power.