What Size Generator Do I Need? A Guide to Choosing the Right Generator for Your Home

Power outages are inconvenient and nerve-wracking in any situation, but when they persist for days or even longer, they can be disastrous. Prepare for power outages by answering the question, “What size generator do I need?”

An emergency generator is your lifeline to keep the lights on and power all of your essential devices, systems, and appliances in the event of an outage. These come in various types and sizes, so it’s important to consider which will be the best solution for your home. Use this helpful guide to determine the best generator size for your home.

Generator Wattage Guide

Use this handy guide to determine the necessary wattage of your generator.

1. Calculate the Right Size Generator For Your Home

Generators come in different wattages, and various types of generators suit different energy needs. Smaller generators can provide power for a few select appliances, while whole-home generators have the capacity to supply electricity to an entire household. These are the main factors to consider when selecting the right model for your home.

Appliance Wattage

The first step in finding the right size generator is to make a list of your must-have devices and electronics, including items like refrigerators, air conditioners, lights, and essential electronic devices. Then, check the wattage ratings of these appliances, which can typically be found on their labels or in their user manuals. Keep in mind that different modes or settings may consume varying amounts of power. Finally, add up the wattage of everything on your list to determine the total power you’ll need to generate during an outage.

For reference, here are the average power ratings of the most common devices and appliances.

Starting, Running, and Surge Wattage

When determining what size generator you need, it’s essential to understand three different power ratings: Starting, running, and surge wattage. The wattage, or power output required by the generator, depends on the type of devices and appliances it needs to operate.

A local home generator installation pro can break down the numbers and help you find the best fit for your home’s energy needs.

Starting Wattage

A generator’s starting wattage is the power needed for an appliance to initiate its operation. Typically, the starting wattage is two to three times higher than the running wattage, which is the power required to keep the appliance running continuously. Keep in mind that many electronic devices and appliances demand higher wattage during start-up and lower wattage to continue operating. 

When a power outage occurs, a generator needs to adjust to the surge in power demands from appliances that run continuously, including HVAC systems, water heaters, refrigerators, and more. If additional appliances like space heaters or microwaves are active during the outage, the generator will need sufficient wattage capabilities to power those as well.

Running Wattage

Running wattage, also known as rated wattage, is the amount of electricity necessary to maintain the continuous operation of an electronic device or appliance. Manufacturers often specify running wattage in the user manual or on the device or appliance itself. If the running wattage is not specified on the device or appliance, you can approximate it using the following formula: Watts = Volts x Amps.

Surge Wattage

Surge wattage represents the maximum amount of power a generator can deliver. If all of a home’s appliances and devices are expected to run off the generator, it’s a good idea to add a buffer of roughly 2,000 watts to ensure everything is covered.

2. Frequency of Generator Use

Another important point to consider when choosing a generator size is how often you expect to use it. If you live in an area with frequent outages or have high energy needs, you may want to consider large whole-house generator sizes with greater capacity. 

Portable generators can come in handy for rare, infrequent outages or the occasional camping trip, but they’re limited in their capabilities. For example, portable generators can’t get wet, so if you live in an area prone to inclement weather, you won’t be able to hook the generator up to your house and use it safely until the winds and rain subside. Furthermore, as these typically run on fuel, running them for extended periods of time can be costly.

3. Types of Generators

Generators come in various types, including portable, inverter, and standby or whole-home generators. The generator type you choose can impact the size requirements or limit your options.

Portable Generators

Portable generators are versatile and come in a range of sizes. These units are the smallest and most cost-effective choice, capable of powering one or two essential appliances or devices during an outage. Some smaller portable generators are also convenient for camping and outdoor activities.

Inverter Generators

Inverter generators are more compact and efficient than standard portable generators. These generators provide clean and stable power, making them suitable for sensitive electronics. Choosing between an inverter generator vs. a standard portable generator will mainly come down to your budget. Inverter generators perform better, but they are typically more expensive than standard generators.

Standby or Whole-Home Generators 

Standby generators, sometimes called whole-home generators, are larger, permanent installations that can power your entire home. They are typically more powerful and come with an automatic transfer switch for seamless power restoration. If you live in an area with frequent outages, have important medical equipment to keep powered, or have greater power demands, investing in the cost of a whole-house generator will be your most reliable solution.