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Portable gensets are currently available for sale in the power range from 500 watt to 17.5 kW.
BASIC FEATURES and SPECIFICATIONS
When choosing a genset, consider the following main characteristics.
OUTPUT POWER.
Manufacturers usually specify running watts and starting watts. The former is the amount of power the genset can produce
continuously, the latter is the short burst of power it can produce to run appliances whose surge current can exceed steady state current. Note that manufacturers often advertise their gensets by starting watts rather then by running watts. Also note that single-phase gensets are usually rated for loads with power factor PF=1, that is for loads with volt-amps equal to watts. Since all motor-driven appliances (such as refrigerators and air conditioners) as well as old computers and electronics without power factor correction have relatively low PF, their VA may be 25-70% higher than their nameplate wattage. For more information, see Generator Wattage Guide.
FUEL TYPE.
Depending on the model, genset's engine can run on gasoline, diesel, commercial propane, natural gas, and bio-diesel. Some models can use multiple fuel sources. Your choice of fuel should be determined by how you are going to use the genset and how often. Gasoline models are generally the least expensive. However, this is probably their only advantage. There are plenty articles around written by various "experts" suggesting to get a gas-powered portable generator as a part of a disaster preparation. In reality, a gasoline model may be a good choice on construction sites and camping trips, but it is not intended for a long-term emergency. If you are looking for a backup power device for a possible major blackout, the main factor to consider is how are you going to keep your emergency source fueled.
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The problem with gasoline is the challenge of storing. Its fumes are highly flammable, which makes storing of large amount of gas unsafe. The NFPA fire code allows storage of no more then 25 gallons of gasoline in residential buildings. A 5000W generator at full load will consume this amount of fuel in about 25-30 hours. Since during a wide-spread power outage gas pumps may not work, you may quickly run out of fuel. Also note that gasoline has a typical shelf life of about six months, although some stabilizers are claimed to extend it for up to 2 years.
Propane, diesel and natural gas are better choices for emergency fuel. As opposed to gasoline, large quantities of diesel and propane can be stored safely in large containers, and they deteriorate much less over time than gasoline.
Propane has practically unlimited shelf life (well, at least 2 years) and is
the only type of fuel that does not require electricity for a refill. Although home improvement stores carry mainly gas gensets,
propane models can be found online. Diesel is less flammable than gasoline. It likewise may be not available during a widespread blackout, but it can be stored in large tanks. Diesel gensets are the most efficient and reliable of all types, but they are also the most expensive.
I am not aware of any devices designed specifically to work on biodiesel, but today's diesel gensets will usually run on biodiesel as well.
Natural gas can assure practically unlimited run time, but it is used primarily in permanently installed standby devices. Natural gas powered portable gensets are rare, relatively expensive, and need professional installation of the fuel line, which defeats the purpose of portability.
For non-emergency applications price may be the main factor in choosing the right model, in which case a gasoline genset may be your first choice. For a disaster preparation however, the main considerations should be given to the convenience of fuel storage and fuel availability during an emergency. In this case, the preference should be given to diesel and propane. For brand name ratings and comparison chart see Portable Generators Review. |
