How to Buy a UPS

Here we discuss the key considerations when planning to buy a UPS for back up Power requirements.

UPS Back up

1. Appliances on UPS.

The first thing to decide before selecting a UPS are the appliances and devices that would be on UPS under Power off conditions. So, the summation of the number of devices and the maximum Power consumption of each device would give the minimum amount of Power Output that the UPS needs to supply under Power off conditions, along with the number of Sockets that can suffice the Power requirement for multiple connected devices. It’s important to understand the concept of True Power in Watts and Apparent Power in Volt Amperes(VA). The ratio of the two is called Power Factor. We’ll not get into how and why True Power is always less than the Apparent Power and the difference between impedance and resistance. But the industry de-facto is True Power delivered to the appliance is 60% of the Apparent Power that the UPS can deliver.

This along with the amount of time that the UPS needs to supply power can provide a value of the overall Wattage requirements from the Battery inside the UPS or connected externally to the UPS.
This coupled with the type of wave the UPS is specified. True Sine Wave, Approximation to a sine Wave or Simulated Sine wave. Sensitive appliances and equipment should consider only a Pure Sine wave UPS. Many devices don’t bother with the quality of AC provided by the UPS because a good appliance design would cope up with any type of AC power supplied. However there are devices that wouldn’t cope up with the bad input Power. Therefore you need a True Sine Wave UPS.

2. Indicators.

Various LED indicators provide indications about the status of the UPS, so if any action is required by the user.
– Online Indicator : The UPS is in the bypass mode and the devices are connected to the mains.
– On Battery : The UPS is providing power to the connected devices. usually this is accompanied by a beep sound every few seconds.
– Overload : The battery in the UPS is not able to provide sufficient power that the load demands.
Other indicators like UPS Fault and Battery replacement would call for servicing by the manufacturer personnel.

3. Alarms. 

Like indicators provide visual indications, Alarms beep on account of certain conditions.

– On Battery : Power is provided by the UPS when the mains is powered off.
– Low Battery : Battery is at it’s threshold supplying current and needs a recharge for further UPS operation.
– Overload : The load draws more current than the battery is specified at. Either a higher Power UPS is to be considered or disconnect appliances from output as feasible.
– Over Heat : The work done by the UPS has increased it’s temperature beyond specified limits and needs to cool off.
– UPS Fault : There is wiring fault like reversed polarity or ground wire missing etc.

4. ROHS Complaint UPS.

Restriction of Hazardous Substances compliant UPS parts exclude specific substances, This includes Mercury, Cadmium, Lead, Hexavalent Chromium etc that cause harm to human body. So, ROHS is a directive that has become a law in most of the European contries following safety standards.

5.UPS with Internal or External Battery.

So, most UPS for IT devices at home like Router, Desktop, Laptop, Wifi Modem would suffice with a UPS with Internal battery. This battery would usually be of 12 Volts supplying current as the specified VA levels.
For other electrical appliances like Microwaves, Heaters, AC, Refrigerators, UPS with external batteries needs to be considered. These batteries demand a simple connection with the UPS. Also 12 Volts output with different AH levels can be connected serially. This increases the overall Voltage Ampere Hours to meet specific time requirements.

Check the One Drop Down All Consumer Electronics Tool and the selection tool for Home IT and Home Appliances.


  1. I have to confess that I knew very little about UPS but I am so pleased I stumbled upon this post because I was not aware of the difference between true and apparent power. Thank you 🙂

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