Generator Sizing Guide

1 List Applications Needing Generator Power

It’s essential to include both starting and running wattage for each item. Starting wattage refers to the initial surge of power required to start an appliance, often higher than the running wattage. This information can typically be found in the owner’s manual or on an information plate on the equipment. Additionally, gathering the continuous and peak power information for all appliances is crucial to understanding the overall power needs.

2 Convert Power Information to Watts

A calculator may be used to convert power information to Watts if necessary. The conversion depends on the type of load, with Wattage = amps x volts for resistive loads and Wattage = amps x volts x load factor for reactive loads.

In simple terms:

• Watts: The real power used by something (like a light bulb).
• kVA: A measurement that includes both the real power (Watts) and some other power that doesn’t do actual work.
• Amps: This is like the flow of electricity.

If you know the kVA and want to find out the Watts, you need to consider something called the “power factor,” which tells you how efficiently the power is used.

So, to get from kVA to Watts, you multiply the kVA by the power factor and then by 1000. If you know the Amps and Volts, you can also figure out the kVA.

These numbers help you understand how much electricity something needs and help you make sure you have the right equipment to power it.

3 Calculate Combined Power Requirements

When planning to run multiple appliances at the same time, such as a bar fridge, toaster, TV, and portable fan, you need to sum their power requirements, resulting in 920W in this example. Then, identify the appliance with the highest starting power, the bar fridge at 600W, and add that to the total, leading to 1520W. If no devices with electric motors are included, simply sum the running power of all items.

A generator with at least 1520W of continuous power is needed to run these appliances simultaneously. However, choosing a generator with more than the minimum required is advised to avoid overloading and ensure that the appliances can be started or run when needed.

4 Consider the 80% Rule

When selecting and using a generator, it’s important to take into consideration that most generators can sustain only 80% of their maximum power for an extended period. If you continuously operate your generator at over 80% of its capacity, you risk shortening its lifespan and potentially damaging its appliances. Therefore, while it’s essential not to choose a generator that’s too large for your needs, it’s wise to select one that’s slightly more powerful than required. This will provide a buffer, ensuring that you don’t push the generator too hard, preserving its life and protecting your connected devices.