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Finding out what Generator Size is suitable for your needs.

Getting a generator that can meet all of your power generation needs is one of the most critical aspects of the purchase or rental decision.

Whether you are interested in the main power supply or the backup power supply, if your new generator does not meet your specific requirements, it will be of no benefit to anyone as it will cause undue stress or even equipment damage along with the devices connected to it.

Unfortunately, accurately determining the size of the generator to obtain is often very difficult and involves many factors and considerations.


The choices between single-phase, three-phase, kW, KVA, welder, backup, or electric start generator can be confusing. To avoid such confusion, this article aims to help you better understand how the sizing process works and a few key things to keep in mind.

This is not a substitute for a certified electrician. We always recommend that you talk to our in house electricians/technical team before buying or renting, but it should provide you with enough information to have an in-depth understanding of some of the key issues involved.

Generator size changes:
With the latest developments in electrical engineering, generators are now available in a variety of sizes. Generators ranging from 5kW to 50kW are easily available in the household and personal use markets, while industrial generators range from 50kW to more than 3 megawatts.

The convenient portable generator set is suitable for homes, mobile homes and small offices, but constructions sites, plants, large enterprises, data centers, buildings, factories and industrial applications need to use larger industrial generators to meet their higher power requirements.

Generator size-how much power required?
Many people think that smaller generators can be used as backup power sources because they are not always running. This is not just a myth, it can actually be very destructive. Unfortunately, undersized generators are one of the most common mistakes buyers make.
Not only does it bring the risk of damaging new assets (generators), but it also damages other assets connected to it, causing dangerous situations, and even limiting the overall productivity of equipment and/or businesses that rely on it. At least, here to remember the key point is that more is better than less.

How to determine the right size motor or generator?

Although there is no substitute for having a certified electrician inspect and calculate everything for you, the following guidelines provide some good starting points and should at least get you in the right direction:

Know Your RequirementsGoing to a dealer and buying the best or cheapest generator available without any other consideration is clearly not the best approach. It is always better to delve deep into your power generation requirements before making a choice. You can do this in the following ways:

  • Make a list of the items that need to be powered by the generator
  • Make a note of the starting and running wattage of the respective items
  • Calculate the total power requirements in KVA or KW

Finding Starting and Running Power: Getting the correct starting and running power for the equipment to be powered is critical to calculating accurate power requirements. Generally, you will find this information on the nameplate or in the owner’s manual in the buyer’s kit for each device, tool, appliance, or other electrical equipment.

Ampere-watt conversion:
A tool’s power requirements are often expressed in amps. To convert the power requirement of the tool from amps to watts, follow these calculations, or you can also use our convenient conversion tool on our energy calculators web page.
For resistive load: Watt = Ampere x Volt
For reactive load: Number of Watts = (Ampere x Volt) x Load factor

Power demand graph: It often happens that you lose the user manual or cannot find it for some reason reason Power specification requirements for tools and / or other electrical equipment in operation. This is an example of a power consumption chart showing some typical wattages used in common tools and appliances.

This power consumption chart is provided as an example only to illustrate the difference between starting and operating wattage, and how each device has specific power requirements.
If you have any questions about a particular project, you can contact the manufacturer, consult an electrician, or contact us for a free consultation.

Different ways of Calculating:  Depending upon the type and number of devices, and the way the generator is scheduled to be used, there are a few different ways of calculating power requirements:

  • Single motor running 
  • Multiple motors running simultaneously
  • No electric motors

Advantages of choosing the right size generator: Now that you have an idea on how to choose the appropriate size of generator to suit your needs, here’s just a few of the benefits obtained by going through that process:

  • No unexpected system failures
  • No shutdowns due to capacity overload
  • Increased longevity of the generator
  • Guaranteed performance
  • Smoother hassle-free maintenance
  • Increased system life span
  • Assured personal safety
  • Much smaller chance of asset damage

Possibility of asset damage is greatly reduced for all parties, the main and sub contractors and service provider: Because you are not the only one buying a large amount of company assets, and it is likely to be the primary asset or emergency power you need to rely on. At some point you may be in a crisis, deciding where to buy is also a key consideration that cannot be ignored. Over here at Choo Huat Engineering Ptd Ltd, our  technical team with many years of experience would be able to size your generator for you and consider factors such as our diesel saving generators.