What Size Standby Generator Do I Need

Are you tired of experiencing frequent power outages? If so, investing in a standby generator could be the solution you need. But determining the right size for your standby generator can be a daunting task. You don’t want to end up with an undersized generator that can’t meet your power needs, nor do you want to overspend on a larger one. In this article, we will guide you through the process of determining the perfect size standby generator for your home or business, ensuring that you have a reliable source of power during outages.

Determining Your Power Needs

Understanding Your Power Consumption

Before you can determine what size standby generator you need, it’s important to have a good understanding of your power consumption. Start by taking a look at your monthly electricity bills and identify your average usage in kilowatt-hours (kWh). This will give you a baseline for your power needs and help you calculate the appropriate generator size.

Identifying Essential and Non-essential Appliances

Next, you’ll want to make a list of all the appliances and equipment in your home or business that you consider essential. These are the items that you absolutely need to keep running in the event of a power outage, such as refrigerators, medical equipment, and security systems. It’s important to prioritize these appliances, as they will have a higher starting wattage requirement than running wattage.

On the other hand, non-essential appliances, like televisions, air conditioners, and lights, may not be as critical to keep running during an outage. While it’s nice to have these items powered, they won’t be as high of a priority when determining generator size.

Calculating Starting Watts and Running Watts

When it comes to generators, it’s important to understand the difference between starting watts and running watts. Starting watts refer to the amount of power an appliance or piece of equipment requires to start up, while running watts refer to the power needed to keep it running.

To determine the total wattage required, you’ll need to calculate the starting and running watts for each of your essential appliances. This information can usually be found on the appliance’s nameplate or in the owner’s manual. Keep in mind that some appliances may require additional starting watts for a few seconds or minutes before settling into their running wattage.

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Considerations for Generator Sizing

Single or Multiple Appliances

One of the first considerations when sizing a generator is whether you will be running a single appliance or multiple appliances simultaneously during a power outage. If you only need to power a single appliance, such as a large freezer, a smaller generator size may be sufficient. However, if you plan on running multiple essential appliances at the same time, you’ll need to account for the combined starting and running wattage of all the appliances to determine the appropriate generator size.

Power Quality and Voltage Regulation

Another important factor to consider is power quality and voltage regulation. Some appliances, like sensitive electronics or medical equipment, require a stable and reliable power supply. In this case, it’s crucial to choose a generator that can deliver clean power with minimal fluctuations in voltage. Inverter generators are known for their ability to provide high-quality power with stable voltage, making them a good choice for powering sensitive devices.

Frequency of Use

The frequency of use is another aspect to consider when determining your generator size. If you live in an area with frequent power outages or plan on using your generator regularly, you may want to size up to ensure it can handle the load consistently. On the other hand, if you only experience occasional power outages or plan on using the generator sparingly, a smaller size may suffice.

Choosing the Right Generator Type

Portable Generators

Portable generators are a popular choice for many homeowners due to their versatility and affordability. They are typically powered by gasoline or propane and can be easily moved around. Portable generators come in various sizes, ranging from small units that can power a few essential appliances to larger models that can handle a greater load. These generators are a good option if you need temporary power during an outage or for outdoor activities.

Inverter Generators

Inverter generators are known for their quiet operation and clean power output. They utilize advanced technology to produce electricity with low total harmonic distortion, making them ideal for powering sensitive electronics. Inverter generators are more fuel-efficient than traditional portable generators and can adjust their engine speed based on the required load, resulting in improved fuel consumption.

Standby Generators

Standby generators are designed to provide backup power for an entire home or business during an outage. These generators are permanently installed outside the building and are connected to a natural gas or propane line. Standby generators come in various sizes and can automatically detect a power loss, starting up within seconds to ensure a seamless transition. They are typically more expensive than portable or inverter generators but offer the convenience of whole-house backup power.

Factors Affecting Generator Size

Climate and Weather Conditions

The climate and weather conditions in your area can play a role in determining the appropriate generator size. If you live in a region with extreme temperatures, such as very cold winters or hot summers, you may require a larger generator to handle the increased load. Additionally, if your area is prone to storms or hurricanes, it’s important to consider the potential duration of power outages and select a generator that can provide sufficient backup power for extended periods.

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Altitude and Fuel Efficiency

Altitude can impact the performance of a generator, especially if you live at higher elevations. As the altitude increases, the air becomes thinner, which can affect the engine’s ability to generate power. It’s important to choose a generator that is rated for the altitude at which it will be operated to ensure optimal performance.

Additionally, fuel efficiency is another important factor to consider when sizing a generator. Generators that are more fuel-efficient will provide longer run times and require less frequent refueling. This is especially beneficial during extended power outages when fuel availability may be limited.

Average Load Demand

The average load demand is the amount of power your home or business typically requires on a daily basis. Consider factors such as the number of occupants, appliances, equipment, and lighting in your space. By understanding your average load demand, you can ensure that the generator you choose is capable of meeting your power needs.

Estimating Standby Generator Size

Step 1: Identify Essential Appliances

Start by creating a list of your essential appliances and equipment, prioritizing them based on their importance during a power outage. This list may include items like refrigerators, sump pumps, medical equipment, and water heaters.

Step 2: Determine Starting and Running Watts

For each essential appliance, determine the starting watts and running watts. This information can often be found on the appliance’s nameplate or in the owner’s manual. If this information is not readily available, you can use a wattage estimation tool or consult with the manufacturer.

Step 3: Calculate Total Wattage

Add up the starting wattage and running wattage for all your essential appliances to determine the total wattage required. This total will give you an idea of the generator size you’ll need to adequately power your essential appliances during an outage.

Generator Sizing Chart

Reference Table for Appliance Power Consumption

To make it easier to estimate your power needs, reference tables are available that list the typical power consumption of various appliances. These tables provide a general idea of the starting and running watts for common household appliances. However, keep in mind that the specific power requirements can vary depending on the model and brand of the appliance.

Example Calculation

Let’s say you have a refrigerator with a starting wattage of 1,200 watts and a running wattage of 150 watts, a sump pump with a starting wattage of 2,000 watts and a running wattage of 800 watts, and a water heater with a starting wattage of 4,000 watts and a running wattage of 3,000 watts.

Adding up the starting wattage (1,200 + 2,000 + 4,000) and the running wattage (150 + 800 + 3,000), you would have a total wattage requirement of 11,150 watts. This would give you an idea of the generator size needed to power these essential appliances.

Choosing the Right Standby Generator

Consider Generator Capacity

When selecting a standby generator, consider the generator’s capacity in terms of its kilowatt (kW) rating. The kW rating of a generator indicates the amount of electrical power it can produce. A higher kW rating means a larger generator and the ability to handle a greater load. It’s important to choose a generator with a capacity that matches or exceeds your total wattage requirement to ensure it can adequately power your essential appliances.

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Selecting the Right Fuel Type

Standby generators can be powered by natural gas, propane, or diesel fuel. Each fuel type has its advantages and considerations. Natural gas is widely available in many areas and provides a continuous fuel supply without the need for refueling. Propane is stored in tanks and offers flexibility in terms of placement. Diesel fuel is known for its long shelf life and is commonly used in commercial applications. Consider factors such as fuel availability, cost, and convenience when selecting the right fuel type for your standby generator.

Assessing Installation Requirements

Standby generators require professional installation to ensure proper operation and compliance with local building codes. Consider the space requirements, zoning regulations, and any necessary permits when determining the installation feasibility. It’s also important to account for the necessary transfer switch, which connects the generator to your electrical panel and manages the flow of power during an outage.

Additional Considerations

Safely Operating a Standby Generator

Safety should always be a top priority when operating a standby generator. Follow the manufacturer’s instructions for proper installation, maintenance, and operation. Ensure that the generator is placed in a well-ventilated area, away from flammable materials, and that it is properly grounded. Regularly inspect the generator for any signs of damage or wear, and never attempt to modify or repair it yourself.

Maintenance and Service Requirements

Generators require regular maintenance to ensure optimal performance and longevity. This includes tasks such as oil changes, filter replacements, and battery inspections. It’s important to follow the manufacturer’s recommended maintenance schedule and guidelines. Additionally, consider the availability of service and parts for the generator you choose, as timely repairs and replacements may be required in the future.

Factors Impacting Generator Lifespan

Several factors can impact the lifespan of a generator. These include the quality of the generator itself, the frequency of use, the maintenance performed, and environmental conditions. Selecting a high-quality generator, adhering to proper maintenance practices, and protecting the generator from extreme weather conditions can help maximize its lifespan.

Consulting a Professional

Benefits of Professional Generator Sizing

While it’s possible to estimate your generator size using online tools and reference tables, consulting a professional can provide numerous benefits. A professional generator installer will have the expertise and experience to accurately assess your power needs, taking into account various factors such as load demand, starting and running watts, and specific appliances. They can provide personalized recommendations and ensure that your standby generator is properly sized for your specific requirements.

Finding a Qualified Generator Installer

When it comes to generator installation, it’s crucial to work with a qualified and reputable professional. Look for a generator installer who is licensed and insured, and who has experience in installing standby generators. You can ask for recommendations from friends, family, or neighbors who have already installed a standby generator, or you can contact local generator dealers for referrals.


Determining the right size standby generator for your power needs involves understanding your power consumption, identifying essential appliances, calculating starting and running watts, and considering factors such as appliance types, power quality, and frequency of use. By carefully assessing your needs and working with a professional, you can select the appropriate generator size and ensure that your home or business remains powered during unexpected outages. Remember to prioritize safety, follow maintenance guidelines, and consult with a qualified generator installer for personalized advice.

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Albert Stein

Starting this site about today's portable power options was an easy choice as it's one of my passions. Tech changes constantly so you need to make an informed decision before purchasing the wrong products. -Thank you.-

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