What size diesel generator do I need?

Deciding which size diesel generator to choose from is one of the most important decisions made when purchasing a diesel generator.

This is because the size of your generator needs to be suitable for your needs, its use and application. The wrong size may cause issues that are entailed by using an undersized or oversized diesel generator.

When a diesel generator is too large for its use, it may result in various issues such as the glazing of the diesel generator from under-loading, and operational inefficiency. When a diesel generator is too small for its use, it will cause unneeded stress to the generator due to over-loading. This will rapidly increase wear and tear to the generator.

Deciding the most suitable diesel generator with various information such as single phase, three phase, KW, kVA, ampere, voltage, sound level and fuel consumption can be difficult at times.


How To Determine The Right Generator For You?

First you need some information essential information.

Your Total power requirements in kVA or KW;

Whether you require 'Single Phase' or '3 Phase Power'; and

How often you will be using your diesel generator.

By knowing the answers these 3 key questions, you will be able to figure out exactly which diesel generator will be suitable for you and really help you narrow down what you need.


Total power requirements in kVA or KW

Determining your total power requirements in kVA or KW should be relatively simple.

Consider all the tools, machinery, and equipment that you will need to be powered by your diesel generator. We recommend you add an extra 25%-35% on top of all the power needed for your tools, machinery, and equipment.

Add all these tools, machinery, and equipment power requirements up and with your 25%-35% extra power on top and this will give you your total power requirements.


Single Phase & 3 Phase Power Requirement

Phase Power refers to how the distribution of alternating current (AC) electric power and the system that it uses. Most devices will be Single Phase or 3 Phase.

This information can usually be found in the information plate of the equipment.

To identify the phase power, you need to look for the voltage requirement of the equipment.

Generally, the following applies:

240V means that it requires single phase power.

415V means that it requires three phase.

Ensure that you use the right phase power for the right generator for it to be compatible.


How the diesel generator being used?

You would first need to understand how the diesel generator being used for does and it can be divided into 3 categories:


  1. Prime application
  2. Standby application
  3. Continuous power supply application



Prime Application

With prime application, you would require the generator to run on a frequent basis; either daily or weekly for 3 – 4 hours a day.

If you’re in this category, you would require a Gogopower 'Premium Diesel Generator' that comes with an engine from a well-known and extremely reliable brand. These include Kubota, Cummins, Stamford and Mecc Alte.

This is because the diesel generator is going to be used on a frequent basis and it is advisable for customer to go with brand that has proven to perform well jobs that are intensive and rigorous.


Standby Application

With standby application, the diesel generator would only perform when the main power supply has failed, and this means you need a temporary source to supply power to your equipment or site.

In this case, the generator would not be needed the majority of the time and will be dormant. However, it must be constantly ready to provide the back-up power. In our experience, we would recommend that potential customers go with Gogopower’s 'Economic Diesel Generator'. They are generally reliable and are highly economic.

Your best interest is to purchase a power generator that is cost-effective given that your diesel generator will rarely be stressed.

Essentially, your diesel generator is only needed when a power failure occurs, or temporary power is needed.


Continuous Power Supply Application

With the continuous power supply application, the diesel generator will be performing 24/7.

Gogopower would usually advise customer to go with our 'Premium Diesel Generator' for the fuel efficiency and high reliability.

This is due to the fact that rigorous usage of the diesel generator will require quality components that will last you a long time, even though they will come at a higher cost.


Diesel Generator Load

For all diesel generators, 60% – 80% would be the optimal load capacity the diesel generator should be performing.

If the generator is loaded with more than 100% of its capacity, it will likely cause damage to engine of the diesel generator.

For example, you need a diesel generator to power your welding machine, which draws 10kVA of power at 3 phase. The ideal diesel generator would be the DP15K5S-AU as it is a 15kVA & 3 phase generator.

This is due to the fact that 10kVA is 67% capacity load of 15kVA and it within the optimal range suggested.

As previously mentioned, we also don't want a diesel generator that is too large, as it will cause the generator to under glaze. This harms the components of the generator. If the generator is performing on a load at less than 50% of the load capacity, it would be considered to be under load.



Sizing a suitable diesel generator for your application is essential to ensure to have the right generator for the right job and a longer life of the diesel generator.

Understanding the correct kVA and Phase Power needed for your diesel generator will ensure that your diesel generator operates as intended and lasts long.

We must note that it is important to maintain your generator as well.

A generator may last until 300,000 hours. If no maintenance is being done on the diesel generator, the generator will end up lasting less than 100,000 hours.

Maintaining the diesel generator is vital for diesel generator to always performing at best and efficiently.

Request a quote from us

For more information about our products or to request a quote, please call us on 1300 975 078/1800 959 143 or visit our website at www.gogopower.com.au