Home generators come in two varieties: portable or standby. The generator you choose to use when commercial power goes out depends on your budget and the number of home electrical devices you wish to power. Knowing the "starting" and "running" electrical requirements of desired appliances will help you decide what size generator is right for you.

Home Generators

Home generators come in two principal categories: portable or standby. Portable home generators are available from 3,200 to 17,500 watts and can handle essential requirements. Standby home generators typically range from 8,000 to 60,000 watts, often with the ability to handle all the electrical requirements of any size home. Home generators run on gasoline, diesel, natural gas and liquefied gas. Gasoline models are the least expensive and most portable. Portable home generators must be rolled out, fueled, manually started and connected to your household load. A standby home generator can start or stop by the push of a button or automatically because it is connected to the house wiring already. When power is restored, the standby home generator will shut off and connect you back to the utility lines.

Home Power Needs

Wattage is the amount of power required to operate electrical items in your home, expressed in watts. Accurately determining the watts for your home power needs will help you select the size generator customized to your home power needs. As of late 2009, expect to spend $500 on a small gasoline generator to more than $50,000 on a commercial standby generator for your home power needs. Installed home generators average $300 to $500 per kW. You will be prudent to engage a qualified electrician to come to your home (this service costs approximately $70) to access your home power needs and make recommendations. Size your electrical load to the generator. Decide what you really want to run with your generator and make a list of these items. Most electrical items have their home power needs on a tag. Add the "starting" and "running" wattage of each of the items on your list to come to a total amount of wattage needed in both "starting" and "running" categories. One practical suggestion: if you have electric heat, have smaller portable heaters you can plug in to avoid the load of a central heating unit. Matching your home power needs to the size generator you choose is not difficult. Take into account the starting power needed for household items you turn on and the running power for the household items that stay on. For example, if you have a generator rated at 10,000 watts, try to hold on to a reserve and not put more than 9,000 watts on the generator at any one time.

Electrical Wattage Requirements

Two key electrical wattage requirements are "startup requirements" and "running power." Many appliances in your home that have a running motor (e.g., refrigerator) require as much as three times the electrical wattage requirements for "startup" than they do to continue "running." You can perform the calculations for the electrical wattage requirements for all the items in your house that you wish to power (retaining a qualified electrician is a better choice). Keep the list of electrical wattage requirements you are going to run off the generator to 20 percent less than what your generator's stated wattage capacity is in order to avoid overloading. To get you started on determining your electrical wattage requirements, fill out a power consumption table (See Resources). Have two values for each electrical item: "startup requirement" and "running power" need.

Source:

Sizing a generator

Selecting a generator

Resource:

Power Consumption Table