It’s important to know how to size your UPS. Whether single or three-phase, there are several important factors to consider when correctly sizing your UPS system. At any time you can consult our Technical Consultants to help you with this via chat, call, or email. We discuss your situation and recommend an appropriate system. Below are some general guidelines you can use to generally size a system. Customers seeking customized Lithium Ion Battery systems should call their representative.

how to size a UPS System, How to Size Your UPS, UPS Power Factor Calculation

Single Phase Loads (120v, 208v)

  • VA = Volts x Amps x (square root of 3)
  • kVA = 1,000 Volt Amps

Runtime Factor: Load VA vs Battery System

  • VRLA battery runtime calculation (see each brochure)
  • Lithium Ion Battery Runtime Calculation (see each brochure)

  • Single Phase Loads Exercise:

    • Volts = 120, Amps = 25 (VxA=VA) = 3,000VA or 3kVA Load
    • Volts = 208, Amps = 30 (VxA=VA) = 6,240VA or 6.24kVA Load

    Three Phase Loads Exercise (120/208v, 208v, 480v):

    • Volts = 208 three phase X Amps = 50, X SR3 = 18,000VA or 18kVA
    • LoadVolts = 480 three phase X Amps = 50, X SR3 = 41,569VA or 41.5kVA Load

    UPS Power factor CALCULATION

    Power Factor (PF) is the ratio of working power to apparent power, or the formula PF = kW / kVA. A high PF benefits both the customer and utility, while a low PF indicates poor utilization of electrical power.

    kW (kilowatts) or Working Power – the “true” or “real” power used in all to perform the work of heating, lighting, motion, server function, etc.

    The equipment used in a data center will list its kW rating on the UL listing plate. You should average or keep in context the cumulative power factor of your data center loads to properly size the UPS system.

    ups power and internal ups loss

    UPS system internal power loss as well as the additional power required for battery charging. UPS efficiency varies between product models and varies dramatically depending on the loading of the UPS. UPS are rarely run at the operating points where their advertised efficiency is provided. A realistic and sufficiently accurate value for UPS efficiency in a typical installation is 88%. Battery charging is a significant but intermittent power consumer. Under normal operation with a charged battery the battery charging load is negligible. However, when a battery has been partially or completely discharged the battery charging power can be on the order of 20% of the rated UPS load. Although this load only rarely occurs, the generator and service entrance must be sized for this load.

    These additional power requirements contribute to the oversized input breakers required for UPS systems upon installation. Load, plus, inefficiency, overload capability, and also the charging of the battery contribute to overall input breaker sizing.

    The UPS must be able to handle full load while also charge the battery system post an electrical outage.

    UPS Turn-Key Installation Options

    Should you wish to outsource your project as a turn-key process. Our team can manage the entire installation of the UPS System to startup. Our team can work with your internal teams or approved electricians. We also may provide our own preferred contractors to estimate the installation. Our team will estimate the rigging, electrical, site restrictions and all the variables around putting the properly sized system into your facility. This proposal will include everything to UPS Startup.


    Members of our team are available to assist in the UPS system selection process. You may provide a list of equipment to us. You may need a walk through with an Electrical contact either provided by us or your own. We will assist every step of the way. UPS sizing review, UPS voltage selection, UPS Battery Runtime options are all important variables in the selection process. Proper documentation of UPS System manuals and technical information are an integral part of the process so that the installation technician or contractor can properly plan and estimate the project.