|How to Select a Residential Generator
Generators come in a variety of output sizes from 12 kW and higher. The best match will depend on the power (wattage) requirements of your home and the available fuel types. Some appliances with electric motors (refrigeration, air conditioners), require up to 2 to 3 times the listed wattage. The generator should be 20% larger than calculated requirements. Also, the additional capacity allows more circuits to be added for future use.
How much power do you need?
Generators produce AC voltage, very similar to the voltage available in your home. However, while your electric utility company produces sufficient power for all of your electric powered devices, a home standby generator is limited in power output directly related to the engine horsepower. The amount of power that a generator can produce is rated in watts. Rated power is less than peak power as certain components lose efficiency when they are heated from use.
To calculate wattage requirements you should determine which devices need to be powered simultaneously and what are the starting requirements. A wattage chart is provided below to assist you. Remember that with simple "power management" techniques, a small generator can provide adequate power for your home or recreational applications.
The wattages listed below are based on estimated wattage requirements. For exact wattages, check the data plate or operator's manual of the item you wish to power.
Additional Power Considerations
Some appliances need a "surge" of energy when starting. This means that the amount of electrical power needed to start the appliance may exceed the amount needed to maintain its use. Electrical appliances and tools normally come with a label indicating voltage, cycles/Hz, amperage (amps) and electrical power needed to run it. Check with your nearest dealer or service center for questions regarding power surges of certain appliances or power tools.
Electrical loads such as incandescent lamps and hot plates require the same wattage to start as is needed to maintain use.
Loads such as fluorescent lamps require 2 to 2 times the indicated wattage during start-up. Loads for mercury lamps require 2 to 3 times the indicated wattage during start-up.
Electrical motors require a large starting current. Power requirements depend on the type of motor and its use. Once enough "surge" is attained to start the motor, the appliance will require only 50% to 30% of the wattage to continue running.
Most electrical tools require 2 to 3 times their wattage for running under load during use. (For example, a 9,000 watt generator can power a 3,200 to 7,000 watt electrical tool.)
Loads such as submersible pumps, air conditioners and air compressors require a very large force to start. They need 3 to 5 times the normal running wattage in order to start. (For example, a 5,000 watt generator would only be able to drive a 1,800 to 3,100 watt pump.)
If the power consumption of electrical appliances exceeds the operating range or if there is short circuit or other problems in the appliances, the AC breaker could trip "OFF" or the rotation of the generator could be abnormally reduced. In this case, stop the generator to see if the power consumption of the appliances is too large and if there is a problem in the appliances.
What type of fuel is best?
This depends on many factors - shelf life, cost, storage location, availability, etc.
Help Determining Your Home Standby Requirements
A homeowner should not attempt to specify and install a power system on their own. We at Air Services stand ready to assist you in evaluating all of your options.