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The Ultimate Guide to Industrial Generator Sizing: What Size Generator Do I Need?

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For every business, there is a generator. Picking the right size for your needs can be tricky since generators come in so many different capacities. Getting the right size generator is essential.

What size generator do I need? This can be a challenging question to answer.

Knowing that your company needs a reliable backup power supply is a given, but how do you choose the right size to support your business needs? This guide should help point you in the right direction.

How to Calculate Generator Size

No matter what industry you are in, many things determine what size generator you should choose. While you can consult a professional if needed, these suggestions and resources should give you ample insight into the process and get you started.

The first step is assessing your requirements. A critical point in understanding what size generator you need is examining how and where it will be put into use and what amount of power and wattage is required.

There is a big difference in selecting a generator that will be used as a power backup versus one that will be used for industrial tools and remote operations. It’s a good idea to make a list of each thing the generator could be used to power and their wattage.

You can narrow down the generator size choices by calculating the total kVA and kW that will be needed. A square foot system is usually used to factor power needs when sizing generators for commercial or retail applications using these formulas:

  • Retail Usage: kW = 50 kW + 10 watts/sq. ft.
  • Commercial Usage: kW = 30 kW + 5 watts/sq. ft.

Why Does Proper Sizing Matter?

You know that under-sizing can be detrimental when you consider all the things a commercial generator may need to power during a blackout. Over-sizing has many dangers, as well. Let’s take a brief look at these:

Too Large

  • Electrical system damage
  • Operational expenses that are wasteful
  • Uneconomical production of power

Too Small

  • Unreliable power
  • Critical equipment and security system failures
  • Overheating and damage to the generator

Generator under-sizing is a common mistake made by buyers, and since we know the dangers, it’s best to get it right.

Location Needs

The next thing you want to consider is on-site needs after getting an understanding of load capacity and power ratings. For example, ask your self these questions:

  • Is the generator needed going to be for standby, primary, or emergency power?
  • Is a portable or station solution better?
  • Are there space or environmental concerns at the location?
  • Is a single-phase or three-phase unit a better fit for my power requirements?

The answers to these questions, fuel type, electrical system connection, generator set duty, and supply rating are essential when choosing the most efficient generator model. You can also consider the altitude and ambient measures, emissions and voltage regulations, and the possible expansion capabilities.

Types of Generators

Commercial businesses often prefer standby generators because they begin operating the moment they detect a power outage. Of course, having a backup power source for emergencies is critical. It lets you continue regular operations without any risk of lost revenue, or health-related accidents (like in a medical facility).

For example, it’s also essential to understand the primary uses of different types of generators, like single-phase versus three-phase generations. Installing a single-phase generator is not a good move for a commercial business and could have disastrous results. Here’s a bit of detail about the two primary types of generators to explain more.

Single-Phase Generators

Single-Phase generators are generally used for residential purposes. They also can be a fit for rural areas where small equipment does need constant high-voltage power and, therefore a single-phase does an adequate job. These generators operate in the range of 120 to 240 volts.

Three-Phase Generators

Commercial businesses generally need a three-phase generator due to their much more substantial power requirements. These generators usually operate at a voltage of 480.

Three-phase generators have these properties:

  • Commonly used for high-density data-centers
  • Typically costly to convert or upgrade from a single-phase setup
  • Less cost-intensive wiring, lower voltages, is safer and overall less expensive to run
  • Higher efficiency when equipment used is made for this type of generator

Fuel Types and Sources

A primary concern when buying a generator is what type of fuel it requires. Generally, there are few options including gasoline, diesel, propane, natural gas, and even solar energy.

To understand primary points of three of the common fuel choices, we’ve put a list together:

Diesel Fuel

Diesel generators are found in commercial businesses like hospitals and 911 call centers in addition to facilities with high kW appliances that need a steady supply of electricity to keep running during an urgent situation.

Some of the positives include:

  • Easy to obtain
  • Less costly to run and maintain
  • Diesel is the least flammable which makes it great for storing a supply on-site

Some of the negatives include:

  • Shelf life of only 18 to 24 months
  • In colder temperatures diesel is not as effective, requiring generators in cold areas to use another fuel type in addition to diesel
  • Diesel generators are the noisiest option

Gasoline Fuel

Although gasoline is probably the most available fuel to obtain, it is only suitable for generators that produce less than 150kW of electricity. There are also many more safety and cost concerns when using gasoline-powered generators. Some of the negatives include:

  • Short-term shelf life of only 12 months
  • Highly flammable posing safety concerns for keeping a supply on-site

Natural Gas Fuel

Natural gas is often used to fuel entire towns and schools in addition to businesses. It is also the only fuel source that is distributed from a local utility grid instead of on-site.

Positives include:

  • Abundant and easy to get
  • Outperforms other fuels even in cold environments
  • Doesn’t require refueling
  • Long-lasting generator operation

What Size Generator Do I Need?

What size generator do I need? Getting an answer to this question can be a challenging pursuit.

The experts at Swift Equipment can help you to understand some of the more difficult points. Now is the time to reach out with any questions!

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