Ultimate Guide – What you need to know when buying a generator

Atlas Copco QIS generator


Looking to buy a generator but not sure where to start?


Generators can be extremely confusing if you’ve never come across one before. You’re not the only one who doesn’t know where to start, a lot of people don’t know how to choose a generator for their application! But if you are planning on getting one for your site, it’s important you understand the basics and what you actually need a generator for, before you buy one. We’ve put together an ultimate guide to help you get prepared for buying a generator:


Identify your requirements


  • What is the size of your site?

Is it a large data centre or a small warehouse? It’s important to determine how much power you’ll need as to what size of generator you require.


  • What is the exact electrical load of your site?

We can accurately recommend the size of generator you will need, depending on the electrical load of your site. It is important to size your generator to site requirements, taking into account all electrical factors to ensure you have capacity to power everything required.


  • What fuel type are you looking for?

Vital Power are specialists in diesel generators. Depending on your requirements will depend on which fuel type is best for you. On an industrial level we will always recommend diesel as this is the most common fuel type for large industrial applications. 


  • What is the nature of your load requirements?

Do you require your generator to supply machinery within a production line, or is it to power critical healthcare equipment with a hospital? Finding the perfect-fit generator for you depends on what you will be using it for. Start up currents should be considered if you will be running pumps/motors etc.


Different types of generators


  • Open Set

These are typically the cheaper option and are ideal for internal use. Consideration should be made for noise requirements and allowance should be made for air handling/exhaust systems. They are typically easier to maintain.

Open set Atlas Copco generator. Diesel Atlas Copco QIS range generator

Open set generator

  • Canopied/containerised

If your site is noise sensitive, or you need to house a generator outside, then its crucial you opt for the canopied/containerised type. These generators are supplied within noise reducing housings and can be positioned outside.

Containerised generator on roof. Canopied generator on roof

Containerised generator


Difference between kW and kVa


Like most people that are new to the industry, the units of measurements will be the most confusing. Don’t worry though, you’ll find everything you need to know below:

  • Generator size is most often referred to in kVA, which stands for ‘Kilovolt-Ampere’ (apparent power).
  • kW stands for ‘kilowatts’ which you may have heard before. Most electrical bills measure your power usage in kW.
  • Power factor measures the efficiency of your generator. Most diesel generators have a power factor of 0.8.


To work out the efficiency of a generator use this formula:

Apparent power (kVA) x power factor (pf) = actual power (kW)


To work out the kVa of the generator needed, simply reverse this equation:

Actual power (kW) / power factor (pf) = apparent power (kVA)



Don’t worry if you aren’t able to work this out yourself. As long as you know the kW (power usage of your site) then we can determine what the best generator is for you.

We hope this has helped in giving you a basic knowledge of generators. For more information that’s specific to your requirements, don’t hesitate to contact our sales team now. We can walk you through what’s best for you and your site.

Contact us today to see what we can do for you.