How Big Should My Home Generator Be?

2020 was reportedly the worst year for power outages in the U.S., with Americans going at least eight hours on average with no electricity within the year. Unfortunately, it’s also expected that this may get worse. Power outages can be very inconvenient, leaving you with problems such as food spoiling, moving safely around the house in the dark, and keeping warm or cool. So to have essential electronics and appliances up during power outages, you should consider getting a home generator.

But before you go out and buy the first or the most powerful generator you find, it’s important that you know that there are different sizes. Every generator has an alternator with a PCB that has pre-built component parameters. This ensures that the system processes only a certain amount of energy at a given time. This also means it’s important to get the generator’s size right — if it’s too large, you’ll have overpaid for the unit and the cost to operate it. Meanwhile, a too-small generator will be overloaded or forced to supply more power than it can handle. When this happens, it will either automatically turn off, or overheat, which will fry the generator and every appliance connected to it.

So to get a generator of the right size, below are two main factors you’ll need to consider:

Appliances you want to power

In the event of a power outage, would you prefer to power just a few of your appliances, or do you want to power your whole home? List down the appliances, and determine the surge wattage and running wattage of each. Surge wattage, also known as starting wattage, is the amount of power an appliance needs at its start-up. This is typically two to three times higher than the running wattage, which is the amount of power an appliance needs to operate. For instance, a light bulb would have the same surge and running wattage of 60 watts. But a fan will have a running wattage of 75 watts and a surge wattage of 150 watts.

Once you’ve added all the appliance wattage together, use that as a basis for the kind of generator that will suit your needs. So if you end up with a total wattage of 31,560, you should get a 35kW generator. However, if you’re calculating the wattage yourself, keep in mind that this is just an estimate. If you want something more accurate, consulting a professional electrician would be better.

Frequency of power outages

How often and how long you’ll experience power outages is unpredictable. But you can base it on three different scenarios, namely frequent, occasional, and rare power outages. For instance, frequent power outages are sometimes prolonged and are typically experienced in places that see severe weather events like blizzards.

If you fall under this category, you’ll want something that will last longer and can power a lot of appliances. A large inverter generator will be a good option. These generators are more complex than conventional generators since they can get power from the fuel tank, battery, alternator, and inverter. This makes them a more stable source of electric supply. But if you rarely lose power, a midsize or recreational inverter generator will be able to give you peace of mind in case of a power outage.