In the day and age we find ourselves, having an uninterrupted power supply is crucial to any business. With the increasing load shedding and interruptions in our power supply, installing a good quality generator should be at the core of any business plan.


When buying/renting a generator, it should not be stressful to determine a suitable size generator for your business. It would be best to have a power backup supply for commercial and industrial industries to ensure your electrical equipment doesn’t stop working during power failures.


When sizing your building, it’s good to remember the following factors. 

  1. Voltage Sag

Voltage sag or dip is the temporary drop that happens when there’s a short circuit or overload of an electrical motor. Your generator must be able to deal with the maximum allowed voltage sag as it reduces the available voltage, affecting its regulator system.

Consult with an expert to go through the spec sheets to determine the allowable drop in input voltage.


  1. Frequency sag

With all the heavy equipment in an industrial building, there is a high possibility of a frequency dip. It could cause a massive problem due to the average frequency of a generator. Therefore your generator must be able to handle the maximum transient drop in both frequency and speed.


  1. Surroundings of the building

The location of the building plays a vital role in the generator’s performance. The combustion engine needs sufficient air to function correctly. Things to consider during installation include humidity, temperature and altitude of the building.


  1. Power equipment

Not all businesses require the same power supply, and the more powerful equipment will demand more backup power. For example, if your business is remote with no power supply, you will need a more powerful generator and possibly a more significant generator.


How do you size the generator for an Industrial business? 


Once you have considered the above factors, you need to size the building for the generator you need.

Various methods are available to do so, but you should consult with an expert.


  1. Full-load capacity method.

A scientific step that will help you determine the correct size generator. It requires you to take a full-load current measurement during peak sage to establish the generator capacity.

Divide the total amps by 2 (two) for a single phase or 3 (three) for a three-phase current.

Multiply the result by the supply voltage and then by 1000 to get the result in kilowatts.


  1. Full-load capacity by history or Power usage history

Your monthly electricity bill plays a role in determining the size of the commercial generator. Its best practice to work through the past 12 months’ usage and analyse the total power usage to determine the highest peak demand and add a percentage for reserve capacity.


  1. Full-load capacity by motor use or Extensive motor use method. 

This method requires you to determine the starting current for the most powerful motor responsible for turning on and off. Then, multiply the number by the voltage required for watts.

For other motors, multiply the voltage for watts by the current. Then, add the total watts and multiply it by 1000 to get the results in kilowatts. Finally, add 25% reserve capacity to size the generator.


  1. Square foot measurement method

It is one of the best and simplest methods if you are in the retail or restaurant business.

For retail: 50kw +10kw/ square foot

For a commercial building, you must apply 50kw +5kw/ square foot.


Your business’s success or failure lies in your power equipment’s functionality. Get an expert to advise on sizing the correct and most appropriate generator.


Specialists like Africa Power Equipment can assist you by analysing your system and measuring your needs and requirements to make the best recommendations to ensure your business stays powered up and thriving.



*The mentioned size guides are for estimate purposes; you should consult an expert before buying a generator. Power equipment varies depending on make, model, and capacity.

2 Responses

Leave a Reply

Your email address will not be published. Required fields are marked *