September 2022

A Beginners Guide to Uninterruptible Power Systems


Photo of Adam Baverstock - Sales Director

Uninterruptible Power Supply, UPS device, battery backup power supply, critical power backup or backup power systems are some of the different terms used to describe a UPS.

In the first of our blog posts, Specialist Power Sales Director and resident UPS expert Adam Baverstock will touch on everything you need to know about buying and owning a UPS. From how it works, what size it needs to be, where do you put a UPS and much more.

Then in future posts, Adam will go into greater detail about each of the sections in this article. By the end, you will have everything you need. First, we will start with the basics and what exactly is a UPS.

What is an Uninterruptible Power Supply (UPS)

An uninterruptible power supply (UPS) essentially provides backup power in the event of utility mains disturbances or disruptions when your regular mains power source fails, or the voltage drops to an unacceptable and harmful level.

A UPS is a device typically using a bank of batteries that can support the load for a few minutes or several hours. In addition to batteries there are other energy storage options like flywheel and Supercapacitors.

Depending on the topology of UPS, it can also provide some other benefits such as always providing a continuous & stabilised source of supply to the connected load.

View all our UPS products

3D UPS icon from Specialist Power Systems
City landscape with Specialist Power logos

Why You Need a UPS

One of the biggest causes of downtime and data loss in the data driven world we operate in today is utility mains power interruptions.

In the 21st century, where we have become heavily dependent upon the continuous availability of electricity in both our homes and business, a loss of power can be catastrophic.

The electronic devices that we rely on every day for communication, security and entertainment are so important to our day-to-day life that having a UPS ensures that they continue to operate normally and will not be affected by any potential power problems.

Organisations in almost all sectors are reliant on having equipment that will continue to operate seamlessly 24/7/365. Computers, telephones, data storage and many other pieces of equipment require continuous power to maintain productivity and efficiency.

A UPS is a sound investment as it generally protects against Revenue loss, loss of productivity, damage to reputation or even backing up vital life safety systems.

Clock with arrow going around the outside

How Does an Uninterruptible Power Supply Work

Typically, most UPS Systems are made up of an AC/DC Rectifier, DC Battery, DC/AC inverter and static switch (utility mains bypass)

A UPS is an electronic device which sits between the incoming utility mains power supply and the critical equipment, offering a high level of protection from power disturbances.

The UPS, if it’s an online type, also provides a zero-break transfer to battery backup in the event of loss of mains allowing the load to continue to be powered for as long as the battery source lasts.

What Different Types of UPS Can You Buy

When shopping for an Uninterruptible Power Supply, it is important to research and speak to an expert to get the correct size and type of UPS for your requirements.

There are three primary types of UPS systems which are Online/Double Conversion, Line-Interactive and Offline/Standby.



Over 20 Years experience icon with rosette from Specialist Power Systems

Online UPS – Highest level of protection with dual conversion AC/DC rectifier - DC/AC inverter, zero break transfer in event of mains failure, best protection against all common power problems. Nearly all larger scale UPS above 4kVA are typically online double conversion.

Line Interactive UPS – Medium level of protection with basic filtering of voltage and the inverter only comes online in the event of a mains failure with a typical break between 2-6ms. Units generally available between 400VA and 3000VA.

Offline UPS – Lowest level of protection – Typically only provides power backup with the inverter only coming online in the event of a mains failure with a short break of between 6-10ms. Units generally available between 400VA and 3000VA.

We will go into much more detail in our later blog posts but if you wish to find out more on how these types of UPS work then visit our UPS pages.

Does the Size of Your UPS Make a Difference

You will have noticed when browsing our UPS products section, that all UPS devices are rated in either VA or kVA – this is the power rating in volt amperes or kilovolt amperes. This can range from around 400VA which can be used for desk top computers and low power components, up to 800kVA which are typically used in data centres. Several UPS units can be combined and connected in parallel to form larger overall systems.

A UPS must be specified correctly at the outset to cover the day one loads and any future expansion. The higher the capacity of the UPS, the more equipment, and devices it can support. Under sizing could cause problems and lead to potential failure, while oversizing could waste energy, money, and take up more floor space than necessary. 

Electricity bolt with electrical cords around the outside
Free site survey rosette with Specialist Power logo in the middle

We will discuss sizing of a UPS in future posts, but several factors will influence how a UPS should be sized:

  • Combined load of all the equipment the UPS will support
  • Starting currents of equipment
  • Future expansion requirements
  • Battery runtime day one and future requirements
  • Need for redundancy

If you are in any doubt, we would recommend our customers to take advantage of our free site survey before any work is undertaken to make sure that the correct size of UPS is supplied. More details of what we can offer with a site survey can be found further down this article.

Necessary Run Time of a UPS

The runtime of a UPS (autonomy) is the length of time an Uninterrupted Power Supply will last for at a specified load level to keep equipment operating in the event of a mains power failure.

For example, a 10 kVA/8 kW three-phase UPS with a 14Ah battery set will offer approximately 15 minutes runtime at full load. But this would be extended to 30 minutes or more when powering a reduced load at 50% capacity.

How long you need to support equipment will be different for most customers. In some circumstances, runtime only needs to be for a few minutes for a standby generator to kick-in and take over.

On the other end of the scale loads may need to be supported for several hours where extra battery strings connected in parallel will increase autonomy.

As always, we recommend speaking to a UPS expert to make sure you get the correct set up with the necessary runtime for your requirements.

Thermometer icon

Location – Where to Put a UPS

A UPS purchase can be a significant investment for any business which is why it is important to carefully think about the location of where it will be installed.

It is imperative to position your UPS correctly to adequately protect it from any potential hazards such as exposure to moisture, excessive heat and tampering by unqualified personnel. Typically, most UPS Systems are installed in an air-conditioned environment but not always. Most UPS Systems have a wide operating temperature window of between 0°C and 40°C.

Batteries play an integral part and work at their optimum at a constant room temperature of between 20 to 25°C so these would normally always be installed in a temperature-controlled environment. When batteries operate outside of the recommended temperature range, they can rapidly lose their ability to maintain capacity. For every 5°C above 25°C, the lifespan of a UPS battery could be reduced by as much as 50%.

Why a Site Survey Is So Important

A site survey will be carried out by a knowledgeable and experienced team which is essential for any successful UPS installation and is vital at the start of any project.

To make sure you get the correct UPS, the necessary runtime and it installed in the right location, we will send one of our experts and carry out a free survey.

From this survey we assess your requirements to make sure we provide you with the right power protection solution for your business.

Clipboard survey icon with Specialist Power logo

During a site survey we look at the following to make sure your power is supported with the correct setup

  • Asses the load requirements and electrical profile
  • Physical locations and environment of the UPS
  • Delivery route and logistics requirements
  • Discuss any monitoring/communications requirements
  • Look at any electrical works that may be required
  • Discuss different options from various Manufacturers

Do You Need a Monitored UPS

If your business depends on a UPS system to protect power to critical applications, then you may want to think about remote monitoring.

Your UPS can be monitored via an SNMP Network card across your local area network or remotely via SMS or email alerts as an example of some of the most common connectivity options.

We also offer a UPS battery monitoring service to ensure your battery system is under constant review. This acts as an early warning system to any potential battery failure to individual blocks or whole strings.

Computer screen through a magnifying glass
Specialist Power rosette alongside a 3D UPS icon

UPS Servicing and Maintenance

An Uninterruptible Power Supply is a complex piece of electrical equipment, full of parts and components that will age over time and there are occasions when even the most reliable UPS will experience faults or failure. It is at critical moments like these that you will need reliable, expert support to get you back up and running as quickly as possible.

Batteries are an important part of your UPS setup therefore regular testing and maintenance is essential to keep a long-life cycle of your batteries.

Several key components within your Uninterruptible Power Supply have a specified manufacturers’ design life. For example, batteries, fans, and capacitors will all need to be replaced during the life cycle of a modern UPS.

Investing in the right service and maintenance plan is essential to ensure your UPS system is operating effectively. Without regular servicing you run the risk that your UPS might not protect your critical equipment when you need it most.

Having a service and maintenance plan gives you peace of mind if something goes wrong, knowing that you have access to 24/7/365 technical support and guaranteed engineer onsite response times.

Photo of Adam Baverstock - Sales Director

Always Best to Speak to an Expert

I hope from reading our beginners guide to Uninterruptable Power Supplies you will have started to get a better understanding of the complexities around investing in a suitable backup power solution.

Whether it is for a home office or a mission-critical datacentre there are lots of things to factor when choosing the right product which is why we always recommend speaking to an expert.

With over 20 years’ experience in offering UPS sales and service contracts across multiple UPS manufacturers such as Riello UPS, APC, Eaton, Socomec and Vertiv, our technical expertise and knowledge of the power protection business has built us a reputation for uncompromising service excellence and trust from our customers.

Contact us today to find out how we can help with your power backup needs.

Adam Baverstock

Sales Director

Get in touch

Enquire Today

For more information, please call us on +44 (0) 1234 851155 or send us a message below.

More of our blog articles

Why Do You Need an Uninterruptible Power Supply

In our latest blog post, we talk about why a business of any size in any sector needs a reliable Uninterruptible Power Supply.

Read Our Why you need a UPS blog

The Importance of UPS Maintenance

In the latest of our blog posts we talk about why it is so important to support your UPS investment with the correct service and maintenance routine.

Read our importance of maintenance blog

Can Lithium-Ion Become The UPS Battery of Choice

In the latest of our blog posts we discuss Lithium-Ion batteries and why they are starting to appear in UPS product ranges.

Read our Lithium-Ion battery blog