How to Calculate Standby Generator Sizing

When choosing a standby generator, it’s important to understand how the equipment operates. For example, how many watts will your home appliances need to run? This will help you figure out the size of the unit. To determine the power consumption of your devices, you can look at the manuals of big appliances. Then, multiply the wattage in each device by three.

Calculating wattage for a standby generator

To calculate the wattage required for your standby generator, you first need to determine the devices you need to power. You will need to know the starting and running wattage of each device, and then multiply this figure by three to get the total amount you will need.

This wattage number is critical to ensure that your generator is able to supply the power required for all of your appliances. The starting wattage should be high enough to start all devices without any problems.

Starting wattage

There are many factors to consider when selecting the wattage of a standby generator. First, determine how many appliances you’ll be running on the generator. Next, determine how much wattage each one requires in running mode. Then, multiply each one’s wattage by three. Lastly, note down the total wattage of all your appliances.

Generally, the running and starting wattage of a standby generator should be at least double the total wattage of the appliances you’ll be running. This is because some electrical appliances require a high starting load in order to start, but require a lower running load once they’re running. For example, a refrigerator might need 700 watts of starting wattage but only 300 watts of running power.

Running watts

When calculating the running watts of a standby generator, it is important to consider that some appliances require a high starting load, while others only require a low running wattage. For example, a hair dryer requires 1800 watts to start, but only a few hundred watts to keep it running once it has started. Similarly, a refrigerator needs 700 watts to start but only three hundred watts to run on a continuous basis.

Homestandby generators are available in several different sizes and types. The smaller ones are often rated for around 9kW, while the larger ones can handle up to 20kW. They are ideal for small homes and for short-term power backup for mission-critical items. While smaller models cannot power larger homes or provide extended power, they can be a good choice for rural areas with frequent power outages.

Power factor

When sizing a standby generator, the power factor is an important consideration. Power factor measures the efficiency of the generator in converting kVA into usable kW. Generators are typically rated at 0.8 power factor (pf). Power factor is a crucial factor in matching the size of your generator to the size of your load. If you want a 100kVA generator to power 100kW of equipment, the power factor will need to be 0.8 or higher.

In order to determine the proper size of a generator, you must accurately estimate your load requirements. You can calculate this by multiplying the UPS input kW by the demand factor (D). The higher the pf, the smaller the kVa you’ll need for your load. Also, make sure to consider other loads that might require power.

Site access

When selecting a standby generator, consider your load size and running requirements. Your site’s access, including a steep hill or narrow driveway, can also affect the size and delivery of the generator. Taking all these factors into account, you can determine the proper size and model for your needs.


When buying a standby generator, sizing is important. Often, people under estimate how much wattage they will need. This can cause the generator to be overloaded and shut down. This also results in overheating, which can damage the generator. A generator that is too big can also run more expensively, so it’s important to purchase the right size for your needs.

The first step in standby generator sizing is calculating the electrical load in your home. This way, you’ll be sure to purchase enough power to run all of your appliances. Additionally, a backup generator will also help you avoid back-feeding electricity, which can damage electronics and cause fires. You should consult a professional to properly calculate the amount of electrical load you’ll need.