Selecting Your Portable Generator

Portable electrical generators are sized by the amount of watts they will produce when operating. A 2,500 watt generator will supply enough electricity to power twenty-five 100 watt light bulbs for 30 minutes. After that, you should reduce the load by 10 percent to avoid overheating the generator. The total capacity of a generator cannot always be delivered to a single appliance. The power you can deliver to any one appliance is determined by the size of the outlets on the side of the generator.

To power sensitive electronic equipment, you need to purchase the highest quality portable generator you can afford. The quality of electricity produced by different generators can vary. The gasoline engine and the generator must provide consistent, smooth power. Inexpensive motor or generator components can adversely affect electrical power production. Consider purchasing an engine that has an automatic shut off that can detect low engine oil levels. This simple feature will protect your engine from failure. Remember, higher quality usually means higher initial cost. The most economical generator may not be the best long term investment.

When choosing your new generator, you should first make a list of those appliances, lights and equipment you consider to be absolutely essential. For instance, air conditioners use a lot of electricity, so make sure you really need it before adding it to the list. Make sure to note which items you normally run at the same time (for instance, your refrigerator may be running at the same time as your air conditioner).

Most common household items require one or two circuits to run. For example, an air conditioner typically needs two circuits, while a sump pump or furnace requires one circuit. Determining how many items you wish to run at the same time will help determine how many circuits your generator will need to support.

Next, find the wattage of each appliance you want to run by checking the nameplate. Motor-driven appliance may be listed in horsepower rather than watts. I’ve included a table for conversion below. Take note that motors require up to four times as much power to start. For instance, have you ever noticed the lights dim when your refrigerator starts up?

Now that you know the wattage of each appliance and which ones you want to run at the same time (don’t forget to add in lighting) total the wattage. The generator you select must provide that power.

If you get a generator that is too small to run refrigerators and freezers, they will try to start, but the voltage will drop and their motors will overheat and burn out. Consider whether you need a portable generator or if you should step up to a standy-by generator instead.

Motor (hp)		To start (Watts)		To run (Watts)
1/6 1/4 1/3 1/2 1 5 7.5 10		1,000 1.500 2,000 2,300 4,000 18,000 28,000 36,000		215 300 400 575 1,000 4,500 7,000 9,000