What Size Generator Do I Need? How To Choose Generators That Fit You?

A generator is an essential investment for a home or a business site. If you experience frequent power surges and need a solid power backup source, generators are the best option.


Generators can help solve the issue of power cuts. But, when you get a wrong generator home without it meeting your requirements, it is useless. Not only can a faulty generator put undue stress on the unit, but it also damages the devices connected to it.

Since there are variations in generators, a certified electrician can assess all your requirements and suggest buying a generator based on it.

However, through this article, you can adequately understand the size of generators, and which one might fit you.

The Different Types of Generators and Finding the Right One for You

There are different types of generators for various uses. You may have heard of solar generators, which get their energy solely from the sun. But most people widely use generators that run on natural gas, diesel, or propane. Here are three common types of generators to choose from:

  • A portable generator is potent and can provide electricity for various outdoor activities such as camping. Since they are portable, one can easily carry them everywhere. In case of a sudden blackout or storm, these generators can quickly provide emergency power.
  • Whole house generators offer a backup for your entire home. They are hardwired to your house and quickly supply power if there’s an interruption in your regular power grid.
  • Inverter generators have recently become popular as they come under quiet generators, making less noise but having more fuel-efficient than others. These generators are ideal for battery or RV devices as they convert energy from AC to DC power.

How To Calculate the Size Of The Generator?

The owner’s manual has examples of the kinds of structures and devices the generator can provide power.

However, do note that you cannot use smaller generators for standby electric power just because they do not run all the time. Under sizing is detrimental and involves risks such as damaging your generator, the appliances connected to it and creating hazardous situations.

If you have smaller needs, you can calculate the size following these steps:

Note Your Requirements

Without considering your approach, if you go to a dealer to buy the best or cheapest generator, there are chances that the generator may fail to support your needs. So, before making a choice, you need to create the requirements for your power generators.

  • Firstly, make a list of items that need to be powered by the generator.
  • Then, note the starting (energy needed to run on) and running (power required to operate it) wattage of the items. You can find these figures typically inscribed on the equipment, identification plate, and owner’s manual.
  • Lastly, calculate your total power requirements in KVA or KW.

Ampere To Watt Conversion

If your tools are in amperes, convert the power requirement of a device from ampere to watts. Follow this easy calculation to convert the figures quickly:

  • For reactive loads: Wattage = ampere x volts x load factor
  • For resistive load: Wattage = ampere x volts

amps to watts

Load factor refers to the ratio of your electric energy use in kilowatt-hours to peak demand in kilowatts. You can calculate your load factor by consulting your utility bill for data and using it in the below formula:

  • Total kWh for the previous month/ (your peak demand for the period x 30 days x 24 hours)

If you are looking for a specific brand of generator, check out our DuroMax review here.

If you lose the owner’s manual and cannot find the power requirement specification of the electrical devices or tools you are running, refer to online power consumption charts. These demonstrate the typical wattages used in standard tools and appliances.

In this way, you can determine which generator fits right for you, whether diesel or dual-fuel generator and calculate the sizing accordingly.

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My career as an Industrial Electrician with over 20 years experience in maintaining small, medium and very large generators plus repairing small engines and working in an auto electrical shop have placed me in the unique position to provide quality advice on all your generator needs. 😉

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