HOME GENERATORS BASICS
STANDBY WHOLE HOUSE AND PORTABLE GENERATORS-
COMPARISON, REVIEWS, SELECTION GUIDE
home generator.
During an emergency, it allows you to continue using essential appliances such as air conditioners, heaters, refrigerators, as well as lights. Technically speaking, an electric generator is a device that converts mechanical energy into electric energy. The AC power generators for residential applications utilize small engines to produce the mechanical energy. The spinning shaft of the engine is used to create an alternating magnetic field through a coil, which induces electromotive force. Since such a system includes an engine and a generator mounted together, a technical term for this appliance is an engine-generator set or a genset.How to choose a generator.
Home generators can be portable or stationary (standby). They run on a variety of fuels, such as gasoline, diesel, natural gas (NG), and liquefied petroleum gas (LPG). Portable gas models are generally cheap. For example, you can get a 4000W set for about $350. However, such devices have short run time: you would need to refill their tank several times a day if you run them continuously at rated load. In addition to this, they are not suitable as a long-term power backup since gas pumps may not work during a wide spread blackout. For a long term emergency consider standby sets. They can provide continuous power because they are hooked up to an external fuel source, such as natural gas line. Some portable devices can also be fueled from an external source and can therefore provide extended run time too. The main differences between them and stationary sources are in their connection and activation. A portable device has to be rolled out from the storage, filled with fuel or hooked up to a fuel line, manually started, and connected to your loads. A permanent standby generator by contrast can start immediately either by a push of a button or automatically because it is already connected to the house wiring and to the fuel source. Automatic systems have an auto transfer switch that can sense a power outage, isolate your electrical wiring or designated emergency circuits from the grid, and start the genset. When power is restored, such a system will connect you back to the utility lines and will turn itself off. You don't have to be at home to activate it. The typical transfer time of an automatic system is 10-30 seconds. If you run important computer applications, you may still need an UPS to prevent data loss during the transfer time. A UPS will also be useful because even though permanently installed natural gas powered gensets can provide practically unlimited run time, with some engines you will need to shut your system down as often as every 50-100 hours of operation to change the motor oil.In addition to the convenience of an auto starting option and practically infinite run time, permanently connected standby systems offer power levels higher than portables -- their rating ranges anywhere from 3 kW up into hundreds of kW. All this makes them the best as whole house generators in case of a long-term emergency. Although such systems are more expensive than portable and require professional installation, they do increase the value of the house.
When choosing your home system, aside from wattage and cost, consider the duration of time you may need emergency power, fuel availability, safety and convenience of use.
Selecting the fuel.
Your choice of fuel should be determined primarily by the fuels available in your area. Most residential generators are bi-fuel and can run on both natural gas and LPG (casually called propane). You will normally need a simple field adjustment to convert from one fuel to the other. If like most homes your house is already supplied with gas, or if LPG is readily available in your area, a bi-fuel NG/propane genset is your logical choice. See our standby genset review for ratings and characteristics of various systems. Among top brands, the Generac's Guardian® models often have the lowest cost per kW, and in my view are the best buys. An average house with up to 4-ton central air conditioner typically needs a system rated between 14kW and 17kW.When you are selecting a natural gas model, be sure to check its required gas pressure -- occasionally some high power devices may require the pressure to be greater than the standard delivery pressure available to your home. An engine may not work if it is not supplied with the minimum fuel pressure specified by its manufacturer. The typical natural gas pressure in residential installations is 0.2-0.25 psi (6-7 inch water column). If you choose a device that requires greater pressure, find out before you buy it whether your utility company will provide this pressure for you. They will need to install a separate gas meter for the genset or change your existing meter to a higher pressure one. If they change your existing meter, you will need to install an additional regulator to drop the pressure to the normal level for the rest of your appliances. Note that while a stationary NG system seems to be an ideal power backup for the whole house, during a major natural or other disaster the gas supply may be interrupted as well. In this case, you may switch to propane if you built a multi-fuel backup power system.
If natural gas does not exist in your neighborhood, you may install a large propane tank that can be periodically refilled by a local distributor. Propane has practically unlimited shelf life and is normally obtainable during power outages. You may also consider a diesel system. Diesel engines are the most efficient and maintenance-free of all types. However, they are also the most expensive, which makes them more appropriate for industrial applications. In addition to this, diesel, like gasoline, may not be available during a wide spread blackout. For latest deals on some of the top rated residential models see the Discount generators page.
Generator installation.
Normally, a stationary genset is mounted outdoors on a cement pad, preferably near the fuel source. Many models already come with a mounting pad, but you still need to prepare a location that is flat and has provisions for water drainage. To prevent exhaust gases from entering the house, locate the unit in a well-ventilated area away from doors or windows. Due to the heavy weight, you must have at least four people present to unload the device, or request lift gate service when the freight company calls you to schedule the delivery.How to wire your system.
A standby power backup device connects to the house wiring via a transfer switch. The transfer switch prevents "backfeeding" into utility lines (which is dangerous and illegal). It also protects your device from damage by preventing utility power from applying voltage to your house wiring while it is running. In any case, without a transfer switch your genset will likely be overloaded or damaged by the loads of neighboring houses that are served by the same line transformer. Many standby generators come with a pre-wired transfer switch.It is strongly recommended that all electrical connections be done by a licensed electrician. Depending on your local regulations, you may be required to get the installation approval by your electric utility (you may need this certificate if you later sell your house). If you are going to store a large fuel tank, you may also need to obtain a respective permit. The fuel pipe sizing, construction and layout must comply with NFPA 54 for natural gas applications and NFPA 58 for liquid propane applications.
Where to buy.
Buying online has certain potential advantages, such as a broader selection, lower prices, and possibly no sales tax in some states. Among good places to buy at a discount is Amazon's Home Improvement Department. It has the widest selection I've seen yet of Generac, GUARDIAN®, Briggs & Stratton and other top ranking manufacturers, and they often offer free shipping on the gensets they carry. Note that if you buy a GUARDIAN® system, you can order the installation and service from a local GUARDIAN® dealer regardless of place of purchase, i.e. even if you did not buy from them. Of course, you can always hire your own contractor to do the installation.Below you will find additional guides and reviews of residential generators, safety recommendations and other resources you need to make an informed decision about the best emergency backup generator for home use.
SELECTION GUIDES
AND REVIEWS OF
AC POWER GENERATORS
EMERGENCY BACKUP POWER
BASICS
OWNERS REFERENCE-
INSTALLATION, MAINTENANCE, SAFETY
Electric Power Generators- a consumer buying guide
Consumer Reports emergency power buyer's guide: overview, wattage requirements and ratings
How emergency power systems work
Home standby generator- general information, sizing, installation, tips
Home generator wiring and safety guide
Generating set installation guide- unloading, installing, starting
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