How to buy the correct UPS for your system

An uninterruptible power supply or UPS is an invaluable device that can protect your computer from damaging voltage deviations or power failures. Learn how to buy the ideal UPS for your system.

An uninterruptible power supply or UPS is an invaluable device that can protect your computer from damaging voltage deviations or power failures. If your outlet’s voltage drops below a certain amount or rises above a limit it can damage your computer equipment permanently or a series of voltage deviations will wear it down over time. A complete power failure or black is more damaging to your computer and as many people have learned the hard way, all your unsaved work will be lost!

A UPS will protect your computer against dangerous voltage variations and also has a build in battery that will allow your computer to run on for some time if there is a blackout. Below are the three main types of UPS’ on the market.

Offline or Standby System

In this type of UPS, the AC power from your outlet goes directly to your computer and if there is a black out or if voltage crosses the upper (over voltage) or lower (under voltage) safe limit, DC power from the battery is converted to AC using an inverter and that is supplied to your computer. This switchover to battery power usually lasts about 5 milliseconds. If the area you live in suffers from frequent voltage fluctuations, then this UPS will switch between main line and battery power often which will cause the battery to wear down quickly and also lose its charge. These offline systems are the cheapest type of UPS.

Line Interactive System

This type of UPS operates almost exactly like the offline type. AC power direct from mains is used and when there is a black out there is a switch to the battery and inverter circuit. However these units have separate voltage regulators which will compensate for over voltages or under voltages so that it does not have to switch to the battery and inverter. If the voltage goes too low the regulator will increase voltage and vice versa. So it only switches to battery if there is a complete power failure. This allows the battery to last longer (all that switching wears it down!) and it will only drain the battery charge during a black out thus using power more efficiently. These are more expensive than the offline system.

CyberPower CP1000AVRLCD UPS

Online System

In these systems AC power from the outlet is fed directly to the battery via a rectifier (AC to DC converter). The battery then supplies AC power to the computer via an inverter. So basically the computer always runs off the battery and as its charge gets depleted it gets recharged. These systems are used to protect highly sensitive equipment that require the highest levels of power regulation. There is no switching between AC and battery and thus there is an added level of security from power problems. Naturally these systems are the most expensive and are often used to protect expensive IT systems in buildings.

So which of these three types should you get?

For home use a standard offline system will suffice and they come for under $50. However for added safety I recommend going for the line regulated type which have prices starting at about $70 going up to over $200 (much more power). Some neighborhoods have dirty power and these systems are particularly useful then. Line regulated is also called “Automatic Voltage Regulation”. Also check the range of voltages that it regulates, a good range is 90-140V. Some systems will only correct under voltages or only over voltages so double check. You don’t really need to go for the higher end “online” models for home use, they can get quite expensive.

Choosing the correct power rating

You need to make sure the emergency power supply unit you buy can handle your load. You may have a computer, printer, scanner, computer speaks and more to connect to the UPS. Check the rated power (measure in Watts, W) by reading the labels on each device and add them all up to get your total wattage.
You should choose a UPS with at least forty percent more capacity to be extra safe and also because your computer power consumption can go up when you do something processor heavy, play games, burn DVDs etc. Most UPS’ have both a VA (Volt Ampere) and W (Watts) rating. You should be looking at the W rating!

Getting enough backup time and battery replacements

It should say the runtime of the uninterruptible power supply if the power goes out. Just remember at full load the UPS will run for a lot less time than if you have just a few devices connected, so if it says up to xx minutes that is with the lowest load amount. Look for something that will give you enough time to do everything you need. Batteries need replacing once every three years or so. Replacement batteries normally cost between $20 to $40 but can go over a $100 for an advanced model! Ask how much the replacement battery costs when buying one or you might be in for a shock later on!

Extra features on a UPS

Display from Cyberpower CP1500AVRLCD UPS

Today’s UPS’ are quite sophisticated. Here are a few things that might come with the UPS and you might want to look out for.

• Software – This is a feature that comes with most models. Pop in CD provided and you can install a program that will do among other things, check incoming voltages, power consumption, battery life and also save your files and shut down your computer automatically in an orderly fashion if you’re not there.
• LCDs – The higher end models have LCDs from which you can look at battery life remaining, power consumption and incoming voltages among other things. If you have the money to spend why not?
• Surge Only Outlets – Not all the outlets in the UPS may be backed up by the battery. Make sure your unit has enough battery backed outlets for your critical devices (i.e. your computer) and keep that in mind when you hook it up!
• LED’s and Alarms – A good UPS should have an alarm that will go off when the power goes out. Some UPS will allow you to turn this feature off. It should also have LEDs that indicate whether you’re using mains power or battery, whether the battery needs replacing and if there is a UPS fault.

Some of the largest UPS manufacturers include CyberPower, APC and Belkin each with a variety of models with units starting from below $50 to several hundred dollars.