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How to Size a Generator for Your Equipment

Generator Load Calculation: How to Size a Generator for Your Equipment

Choosing the correct generator size is one of the most important decisions when designing a mobile power system. Whether you are powering a food truck, mobile medical vehicle, command trailer, or specialty service vehicle, selecting the right generator ensures your equipment runs efficiently and reliably.

Many businesses underestimate their power requirements or choose a generator based only on rough estimates. An undersized generator can lead to overloads, overheating, and equipment shutdowns. On the other hand, an oversized generator may operate inefficiently and create issues like wet stacking in diesel engines.

Understanding generator load calculations helps ensure that your generator provides consistent prime power while maintaining long term reliability.

In this guide, we will explain how generator load calculations work and how to determine the right generator size for your equipment.

Understanding Generator Power Ratings

Before calculating generator size, it is important to understand how generator power is measured.

Generators are typically rated in kilowatts (kW) or watts (W).

For example:

PowerTech generators are prime rated, meaning they are designed to supply continuous power for daily operations in demanding mobile applications.

Prime power ratings are important for businesses that rely on generators as their primary source of electricity rather than as emergency backup power.

Step 1: Identify All Electrical Equipment

The first step in sizing a generator is listing all electrical equipment that will be powered by the generator.

This includes every appliance, device, and system that will draw power.

For mobile applications, common equipment may include:

Food truck equipment

Mobile medical equipment

Specialty vehicles and trailers

Every electrical device consumes power measured in watts or amps.

Most equipment has a nameplate label showing its power consumption.

Step 2: Determine Running Watts

Once you identify the equipment, determine how many running watts each device requires.

Running watts represent the continuous power required for the device to operate.

For example:

Equipment	Running Watts
Refrigerator	700 W
Deep Fryer	5000 W
Microwave	1200 W
Lighting	400 W
Vent Hood	300 W

To calculate total running watts, simply add the wattage of all equipment.

Example:

700 + 5000 + 1200 + 400 + 300 = 7600 watts

In this case, the equipment requires 7.6 kW of continuous power.

Step 3: Account for Starting Watts

Some equipment requires additional power when it first starts.

This is known as starting watts or surge power.

Motors, compressors, and refrigeration equipment often require higher starting power.

Examples include:

Starting power can be 2 to 3 times higher than running power.

For example:

Equipment	Running Watts	Starting Watts
Refrigerator	700	2100
Air Compressor	2000	4000

When sizing a generator, the generator must handle the highest startup load at any given moment.

Step 4: Calculate Total Generator Load

To determine generator size, combine:

Running watts + starting watts.

However, you only need to account for the largest startup surge occurring at one time, not every piece of equipment simultaneously.

Example calculation:

Total running load:
7600 watts

Largest starting load:
Air compressor startup surge: 4000 watts

Total generator requirement:

7600 + 2000 additional surge = 9600 watts

This means a 10 kW generator would likely be appropriate.

Step 5: Add Capacity for Safety

It is recommended to leave 10 percent to 20 percent additional capacity beyond your calculated load.

This provides several benefits:

Using the previous example:

9600 watts x 1.2 safety factor = 11,520 watts

A 12 kW generator would provide adequate capacity.

Common Generator Sizes for Mobile Applications

Different industries tend to require different generator capacities.

Here are common generator sizes used in specialty vehicles.

Application	Typical Generator Size
Food trucks	12 to 20 kW
Mobile medical units	20 to 60 kW
Command vehicles	15 to 40 kW
Service trucks	8 to 20 kW
Specialty trailers	12 to 40 kW

PowerTech offers generators ranging from 8 kW to 60 kW, allowing customers to match the generator precisely to their operational needs.

Why Oversizing a Generator Can Cause Problems

Some buyers assume that choosing the largest generator possible is the safest approach. However, oversized generators can create operational issues.

Diesel generators operating under light loads may experience wet stacking.

Wet stacking occurs when unburned fuel accumulates in the exhaust system due to incomplete combustion.

This can lead to:

Selecting a properly sized generator ensures the engine operates at an optimal load.

Importance of Continuous Duty Generators

Many portable generators sold for recreational use are not designed for continuous daily operation.

Mobile businesses and specialty vehicles require commercial grade generators designed for prime power operation.

PowerTech generators are designed specifically for:

Unlike off the shelf RV generators, PowerTech units are built with commercial grade components and engineered for demanding environments.

Custom Generator Solutions for Specialty Vehicles

Every mobile operation has unique power requirements.

At PowerTech, generators are custom built to match the electrical load, installation space, and operational needs of each customer.

Factors considered when designing a generator solution include:

This approach ensures that the generator delivers dependable power while maximizing efficiency and reliability.

Use the PowerTech Generator Size Calculator

To simplify the generator sizing process, PowerTech offers an online Generator Size Calculator.

This tool allows users to:

Using a sizing calculator helps prevent undersized or oversized generator installations.

Selecting the correct generator size is essential for ensuring reliable power and long term performance. By understanding generator load calculations and accounting for running watts, starting watts, and safety margins, businesses can choose a generator that meets their operational needs. For mobile businesses, specialty vehicles, and commercial applications, properly sized generators prevent overloads, improve efficiency, and extend equipment lifespan.

PowerTech generators are designed specifically for these demanding applications, delivering dependable prime power wherever your business operates. If you are unsure what size generator is right for your operation, PowerTech can help you determine the best solution for your equipment and power requirements.

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