Buying a UPS is usually accompanied by a litany of questions related to the size, batteries, brand and specifications. With so many brands and models out there in the market, it is confusing to find the right product. Here at Loadshedding.pk we understand your predicament and keeping that in mind, we have put together an easy to understand guide to help you find the right UPS device for your home.
What is a UPS
A UPS or an uninterruptible power supply, also known as an inverter, is an electrical device to provide backup power in the event of a power failure or when there is no electricity on the mains. UPS devices have become a household item in Pakistan ever since load shedding has become a permanent feature. Traditionally UPS devices are used to protect sensitive electrical equipment such as computers and servers from damage and to prevent data loss. As the term suggests, a UPS provides uninterrupted electricity and thus there is no break or gap in the supply in the event of an outage or power failure. This allows connected devices to operate normally without any disruption thus protecting them from any input power interruptions, high over or under voltages.
Due to widespread load shedding in Pakistan, people have to live with 8 to 10 hours without any electricity. In light of this, the cheapest form of power backup is a UPS device. Diesel and petrol generators are very expensive both in terms of upfront costs and upkeep.
The capacity or power rating of a UPS is in VA (volt-amperes). Since power (watts) = current x voltage, watts are also interchangeably used to describe the capacity of a UPS device. Theoretically a 1 kVA system is capable of supporting a load 1,000 watts or 1kilowatt. However due to inefficiencies and the power factor, a 1.5kVA UPS is recommended for supporting the load of 1,000 watts.
Kinds of UPS devices
There are different kinds of UPS devices that exist in the market today. There are two important factors that differentiate various UPS units: the topology and the wave form output. The most common topology that’s used in Pakistan is the Standby Topology due to its entry-level inexpensive nature. However, the type of usage determines the nature of the UPS to be installed. If your usage comprises using computers, laptops or televisions that require pure sine wave AC output, then pure or true sine wave inverters are always recommended. However, if the inverter will be used to power fan and lights in the house, a standard square wave UPS device can be used.
How to select the right UPS?
Calculating your electricity consumption
Prior to selecting a UPS, it’s important to calculate your typical usage or consumption during load shedding hours. This includes lighting, fans, televisions, computers and other low power consumption devices. It is recommended to connect at least one light and a fan per room including an outdoor light to the UPS so that the entire house is functional. Typically you won’t be using all the fans and lights at the same time. In addition, the number of televisions that will be used simultaneously also need to be identified. The purpose of this exercise is to calculate the maximum possible load that will be supported by the UPS. Usually televisions and fans will be drawing more electricity than lights (energy savers and LED lights). Here’s a general configuration for a house where fans, lights, LCD TVs and computers need to be connected to the UPS.
|Electrical Devices||No of Units||Power (Watts)||Total Power (Watts)||Power Factor*||Consumption (VA)|
As you can see that the total power consumption of the above electrical devices is around 1,693 VA or 1.69 kVA. Hence a 2kVA UPS is recommended for this configuration.*Power factor is a measure of how efficiently the electric power is being used in a system. It is usually a number between 0 and 1. Most UPS systems lie between 0.70 to 0.80. We will cover this at length in a separate article.
Finding the right UPS brand
There are plenty of UPS brands available in the market ranging from locally manufactured units to imported ones. It’s important to find a good balance between reliability, quality and cost. Chinese brands such as Homage and Invex offer good value for money and have proved to be quite reliable. Having said that, various local brands have also been functioning trouble-free in many households. Usually local brands use either indigenous circuitry as opposed to chips that are used in Chinese and other imported brands such as APC.
In Pakistan people usually don’t pay much heed to the brand and go with the most cost effective solution. Typical 1.5kVA locally assembled inverters cost between PKR 13,000 to 15,000. These are modified sine wave inverters, which can support televisions and computing devices. 1.5kVA Chinese models such as Homage and Intex will cost around PKR 20,000 depending on the waveform output (true sine wave, modified sine wave etc.). Please note that most inverters that are sold as pure sine wave don’t actually generate a true sine wave like the one that is generated from the electricity at your mains by the distribution company. However, all household appliances run perfectly well on a modified sine wave UPS devices so it is not a cause for concern. Check out our UPS Price Guide to help you decide which models fit your budget.
Selecting the right battery bank
Your battery bank is the most important component of your UPS setup. Batteries are also fairly expensive, especially if you have a larger battery bank consisting of more than two batteries. Batteries come in different storage capacities and types. At the fundamental level, batteries are available as dry and wet batteries. Wet batteries contain a liquid electrolyte in comparison to dry batteries, which use a gel.Wet batteries are commonly used in most UPS systems here in Pakistan because of their low upfront costs in comparison to dry batteries, which cost at least twice as much in similar capacities. Most UPS systems in Pakistan have 12V batteries connected in parallel for larger storage capacity resulting in more backup time.
Storage capacities of batteries are rated in Ampere Hours (AH). So a 150AH battery can discharge at a rate of 150 amperes per hour. If the rate of discharge is 25 amperes, a single 150 AH battery should last you around 6 hours. However, with wet batteries or lead acid batteries, increased load can adversely affect the performance and condition of the battery due to the resultant heat dissipation. The level of charge of the battery also reduces the performance of a battery and may cause in permanent damage. That’s why, regular maintenance of wet batteries are recommended.