How to Size a Home Electric Generator

A home electric generator is a valuable addition to just about any home, but even more so if you live in an area that suffers from extensive seasonal storms. In these areas, it is not uncommon to be without power for days at a time. Having a reliable and properly-sized electric generator will help you get through those difficult days until the power company is able to restore the electricity to your area. There is a fine line, however, between purchasing too much generator and not enough. Here is how to properly size a home electric generator.

Difficulty: Easy

Instructions

Things You'll Need:

• Ammeter (if necessary)
• Pencil and paper
• Calculator

1. Before you head out to the home improvement store to look for a home electric generator, you need to have an understanding of how much wattage your essential appliances are using now. This will give you an idea of what size generator will suit your needs.

2. One way to calculate your wattage is to use an ammeter. The ammeter is placed in-line with each appliance and it reads the amount of electricity being used by that appliance. You can purchase one and do this yourself, or you can hire an electrician to take the readings for you. Keep in mind that if you purchase the ammeter yourself, it will probably cost less than hiring an electrician and you'll have the ammeter for whenever you may need it again.

3. Once you have all of your appliances and their electricity usage written down, add all of the wattage up. This will be a baseline number for your generator needs.

4. If you don't want to put out the money for either the ammeter or the electrician, you can still find the numbers you need. Each appliance has an informational label somewhere on its body. Find the label (or look in the manuals if you still have them) and look for the wattage number.

5. If watts are not included on the label, find the voltage and amperage. You can determine the watts of the appliance by using the following calculation:
   
   volts x amps = watts

6. Some of the larger appliances in your home require more power to start than they do to run (sometimes as much as three times more). This is important to keep in mind when tallying your wattage needs. Find out which appliance draws the largest startup load and add that difference to your wattage needs. You don't need to add all of the startup differences, only the largest, because the appliances will not all be starting up at the same time.

7. Now that you have your total calculations, add another 20 percent to the number. This will allow your generator a little breathing room and you'll have the power necessary if you add any smaller appliances at any point in the future. It will also help your home electric generator to last longer because it won't be working as hard.

Tips & Warnings

• Choose only from among generators that adhere to emission regulations and feature certain safety features like automatic shut-offs in case of overheating or oil pressure loss.
• Don't use the square footage of your home to "guesstimate" your generator needs.