Generator Sizing and Load Management

How To Determine Your Standby Power Needs

When it comes to ensuring uninterrupted power to your home, it is crucial to understand the power needs of your household. This knowledge will enable you to make an informed decision about how to size and select a home standby generator to best suit your requirements.

To determine your power needs, you must first assess the essential appliances and systems you wish to power during an outage. Start by making a list of these items, including lighting, refrigerators and freezers, heating and cooling systems, water pumps, sump pumps, pool pumps, security systems, medical equipment, etc. Once you have identified the appliances and systems you want to keep running, you can estimate the power requirements for a standby generator.

The power requirements of electrical appliances are typically measured in watts. You can find this information on the manufacturer's label or in the user manual. Add up the wattage of all the appliances and systems on your list to get an estimate of your total power needs. Some devices may require additional surge power during startup. Be sure to account for this in your calculations.

To make things easier, we’ve compiled a list of common household appliances along with typical watts consumed while the appliance is running.

Now that you have an estimate of your power needs, it is time to choose a home standby generator that can meet them. These generators come in a range of sizes, starting from around 7 kilowatts (kW) and going up to 150 kW. The size of the generator you choose will depend on the total power needs you have calculated.

The chart below shows the wattage required for common appliances and other loads:

Chart illustrating kW loads from appliances and other common house loads

Smaller air-cooled generators have Load Management capabilities and offer big savings on overall project costs when compared to a liquid-cooled generator. So, let’s look at how smaller air-cooled generators can help homeowners cover the essentials without breaking the bank.

Understanding Load-Shedding

Load shedding is a term often used in the context of power supply management and is a crucial concept for homeowners to grasp. Load shedding refers to the intentional and temporary reduction of electrical power to certain areas or devices during periods of high demand.

A Load Management Module can automatically shed non-essential high loads such as a second air conditioner, clothes dryer, or oven. By shedding non-essential loads, smaller air-cooled generators can maintain stability to avoid overloading the generator.

Load Management

Load management systems, also known as load controllers, are an integral part of Cummins air-cooled home standby generators. These systems ensure that the power generated by your standby generator is efficiently distributed to the essential appliances and devices in your home during a power outage.

It’s important to point out that liquid-cooled generators do not have load management capabilities like their air-cooled counterparts. Liquid-cooled generators are sized to accommodate all potential house electrical loads for Whole House Coverage. For example, a 2500 SF home with two 5-ton air conditioners might require a 30kW liquid-cooled generator to run all house circuits including both air conditioners. However, homeowners can save a bundle on project costs by using a 20kW air-cooled generator if the homeowner is willing to run just one air conditioner at a time. This is where the load management capabilities of an air-cooled generator come into play.

Cummins Power Generation offers three air-cooled generator solutions in sizes ranging from 13kW - 20kW, and each can manage up to four heavy electrical loads with optional Load Management Modules as pictured below.

Cummins 50A Load Management Module

Load Management Modules are most often utilized to manage electric ovens, and clothes dryers. This device is not required for managing central air conditioning loads because your installer can make a low-voltage connection to a thermostat.

While a 20kW air-cooled generator may not be powerful enough to run two 5-ton air conditioners at the same time, it can manage the two A/Cs so only one unit operates at a time. When one A/C shuts down, the generator can now run the other A/C.

Effective use of an air-cooled generator’s load management capabilities can save homeowners thousands of dollars in project costs while keeping the homeowner comfortable during a power outage.

Up next, we cover generator Remote Monitoring and Accessories.

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