With today’s blog entry we will discuss other factors to considering when looking to purchase a UPS. We’ve already discussed the various types of UPS and the pros and cons of each. If you missed that article please feel free to review it here:
There are two methods to use when you review the power capacity needed for the UPS. We will cover the method using watts as you can convert between the two methods easily.

Step 1:
Determine all equipment that the UPS will need to power.
Step 2:
Determine the wattage required to run each piece of equipment. Wattage=Volts x amps example: A piece of equipment runs at 120VAC at 2 Amps. Watts=120Volts x 2 Amps or 240Watts
Step 3:
Add up the total wattage for all equipment.
Step 4:
Add an additional 20 percent to cover overload conditions and future growth.

Another measure of UPS capacity that you will see is VA or Volt-Amps. As an example, after going through step 1-4 you know that you need 700 Watts of power out of your UPS. Take your total wattage, in this case 700W and multiple it by 1.43 and you will find that you need a 1000VA UPS.

700 Watts x 1.43 = 1000 VA

If you have been provided the VA and need to know how many watts you will need your UPS to handle. you would multiple your VA by the company’s power factor rating. For instance, in the link below is a 1000VA UPS that we at Energy Technologies offers:


In order to determine the appropriate wattage you would need to follow the below equation.

1000VA x 0.7 power factor = 700Watts

After you have determined the capacity for the UPS you will need other things that you will need to consider are the following:

  1. UPS Form Factor: Will this be a portable UPS, rack mount UPS, or NEMA style UPS?
  2. Size requirements?
  3. Is Battery Backup needed?
  4. Total number of Output connectors needed?
  5. Are there special Environmental or Electrical needs? For instance MIL-STD, FCC, Hazardous Location.
  6. Will you need communication with the UPS? If so, what type?
    Common types include:
    • Dry contacts
    • SNMP
    • RS-232
    • RS-485
    • USB.
  7. Do you need to be able to control the UPS remotely through the communications port?