Power Calculator

The calculators provided below are to help you determine the size generator that would best suit your needs based on what type of business you are running. Please be advised that there are a multitude of factors to take into consideration when generating a generator size as well as the complexity of electrical calculations. The assistance of a certified electrician is recommended. If you have any questions about computing power or would like assistance please feel free to contact us at your convenience.

Power Equipment Calculator


Calculating Ampers (when known you know kVA)


Converting kW to kVA


Converting kVA to kW


Converting HP to kW


Converting kW to HP


Genset size calculator


(genset needed to start a 3 phase electric motor Direct on Line (DOL) start)

Commercial Generator Sizing Calculator

No matter your industry, from oil and gas to hospitality and telecommunications, it’s vital that your facilities operate around-the-clock. For that to happen, you count on your generators to step in and power your operations during scheduled or unexpected power outages. If your generators can’t meet your power demands, however, they can’t run your facility, which is why it’s critical to ensure your company’s generators meet your load requirements, and then some.

That’s where a commercial generator sizing calculator comes in. It helps you convert units and calculate demands at lightning speed.

How to Calculate What Size Generator You Need

Before using a power requirement calculator for generators, you’ll need to gather some data. We recommend you start the process by answering the following questions:

  • What items will the generator power? It’s essential to be thorough when compiling your list. You’ll need to consider every potential item that will run on your generator. If not, you risk under-sizing your generator by miscalculating your power demands. If you can, have your teamwork with you on this question or at least review your list of items.
  • What is the starting and running wattage of those items? If your company has kept the owner’s manuals, you’ll find the starting and running wattage of your hardware in the manuals. Can’t find the owner’s manuals? If you’re aware of the model number and manufacturer, see if the owner’s manual is available online — you can also check the identification plate for the model information. Another option is to use a power consumption chart. The downside to these charts, however, is that they only provide a sample of similar hardware, which is why it’s better to call your equipment’s manufacturer and obtain the actual numbers.
  • What is the total power requirements for these items? After you’ve compiled the data on your hardware’s power requirements, you can total it. You’ll want to use the kilowatt (kW) as your unit of measurement, especially since it’s the standard for commercial generators in the U.S. If your equipment lists its starting and running wattage in amperes, you’ll want to convert it to watts.

How to Calculate Your Total Power Requirements

While the above provides a summary, there are several steps and ways to calculate your total power requirements, which is a critical measurement when using a generator load calculator. Some companies will utilize all the different methods to ensure they receive an accurate number for their total output, as well as spot any potential inconsistencies that could impact their overall results.

Approaches for calculating your total power requirements include:

  • Measure your peak usage in real-time: With a clamp-on ammeter, you can discover the total number of amps your facility’s using on a day-to-day basis. For this measurement, however, you want full-load current measurements during peak usage, as you need a generator that’s capable of powering your operations when demands are at their highest. Depending on your facility’s continuity plan, you may opt to calculate the differing power requirements of a single motor, compared to multiple engines. Aim to take your measurements at each section of your electrical service, and then add the results together.
  • Review your monthly power bills: Another helpful tactic, especially for facilities with distinct seasonal processes and weather, is to go over your monthly power bills. This approach is a quick process, as many utility companies will denote your peak demand on each invoice. As you review your past statements, track your highest peak demands from the last year. Afterward, use the highest amount and add 25 percent to it to account for your reserve capacity.
  • Calculate your facility’s square footage: While select industries are more apt to use this technique, like restaurants and hotels, it offers a helpful comparison to the other data you’ve gathered from your clamp-on ammeter and energy statements. If you already know your commercial facility’s square footage, go ahead and add five watts for every square foot, plus 50 kW. For retail businesses, use 10 watts instead of five.

Now that you’ve compiled your equipment and its power requirements, you’ll want to consider some variables that will affect the results from a power calculator for generators.

What Variables to Consider When Sizing a Generator

While the formula behind a generator power calculator is sound, inputting data that’s incorrect results in a product that’s not applicable to your facility. That’s why it’s vital to consider several variables that have a significant influence on your total power requirements, which affects the size of your generator and its ability to keep your operations steady through outages.

Factors to consider before using a generator load calculator include:

  • Voltage dips: When your electric motors resume, following your generator kicking on, a voltage dip or voltage sag will occur as the motors are drawing more current. While normal, you do not want a 15 percent or more voltage dip, as you risk damaging your generators and your equipment. Plus, with that high of a voltage sag, your generator doesn’t have the surge capability to manage your total power requirements.
  • Phase power: Another factor to think about, before using a generator load calculator, is single- or three-phase power. While both offer benefits, they’re ideal for different applications. Small retail businesses, for example, can often rely on a single-phase power generator to power their store because it’s suitable for smaller applications and doesn’t deliver power at a constant rate. Meanwhile, industrial plants require a three-phase power generator due to their high power loads that demand a continuous flow of power.
  • NEC requirements: While it’s not your immediate priority when using a generator sizing calculator, it’s essential to think about your company’s compliance with National Electrical Code (NEC) standards. If you didn’t note your facility’s safety systems in your initial assessment of hardware that’ll generate power during an outage, include them now and re-calculate your total power output if needed.

After you’ve weighed the above factors, you can plug your data into our single- and three-phase generator sizing calculator.

How to Use a Power Calculator for Generators

Through our power calculator for generators, you can accomplish a few tasks, including:

  • Converting kVA to kW
  • Converting kW to kVA
  • Converting kW to horsepower (HP)

You can also calculate your amperes, plus see the number of kVA’s your generator would need for a three-phase power setup. After you’ve converted any necessary data, you can input your data into our commercial generator sizing calculator. You’ll select whether it’s single- or three-phase, plus your required volts, amperes and power factor. The generator load calculator will crunch the numbers and show you how many kWs you need to operate through outages.

To learn more about how to calculate what size generator you need, visit our blog or contact us today for assistance.

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