A fuel-powered device that can supply electricity to your house during power outages is casually referred to as a 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.
In the AC power generators for home use the mechanical energy is produced by small engines. The way it works is the spinning shaft of the engine creates an alternating magnetic field through a coil, which induces voltage. Since such a system includes an engine and an alternator mounted together, a more technical term for this appliance is an engine-generator set or genset
HOW TO CHOOSE A GENERATOR.
First, let's quickly go over the different types that are out there. Home generators can be stationary (standby
) or portable
. They run on a variety of fuels, such as gasoline, diesel, natural gas (NG), and liquefied petroleum gas (LPG). Not surprisingly, each type has its pros and cons. Portable gasoline models are relatively cheap. For example, you can buy a 4000W set
for about $300. 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 for a long-term power backup since the pumps may not work during a wide spread blackout. For a long term emergency you should consider standby sets. They can provide continuous power for the home because they are hooked up to an external
fuel source, such as NG 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 models 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 fixed standby generator
by contrast is already connected to both the house wiring and the fuel source. Therefore it can start immediately either by a push of a button or automatically depending on the setting you chose.
Automatic systems normally include an auto transfer switch. It can sense a power outage, isolate your electrical wiring or designated emergency circuits from the grid, and start up the genset. When grid voltage is restored, such a system will connect you back to the utility lines and will turn itself off. You don't even have to be at home to activate it. Note that the typical transfer time of an automatic system is 10-30 seconds.
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TO SELECTION, SIZING AND CONNECTING HOME GENERATORS.
Therefore, if you run important computer applications, you may still need a UPS. It can prevent data loss during the transfer time. Note that even though permanently installed natural gas powered gensets can provide practically unlimited run time, you still need to periodically shut them down to change the motor oil. With some engines you will need to do it as often as every 50-100 hours of operation. This is another reason why a supplemental UPS will be useful.
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 5 kilowatt up into hundreds of kW. Such systems also increase the value of the house. All this makes them the best type of whole house generators
for power outages, especially for the long-lasting ones. Of course, they are more expensive and require professional installation, which are their main disadvantages
. If you want something that can be used right away, obviously, a portable
device is your only choice.
So, what to look for when you are choosing a generator for the home? Aside from wattage and cost, the main things to consider are the duration of time you may need emergency power, fuel availability, and convenience of use.
SELECTING THE FUEL.
If you decided to go for a stationary type, your choice of fuel is determined by the source you already use for the home's heating or by the fuels available in your area. Note that most permanent residential generators are bi-fuel and can run on both natural gas and LPG (casually called propane). You may need just a simple field adjustment to convert from one type 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 detailed standby genset review
for ratings and characteristics of various systems. Among major brands, the Generac's Guardian® models probably have the lowest cost per kW. In my view, given their 5-year warranty and a relatively low cost, they are the best buys. You just need to pick the right size. CR magazine's pick in 2013 was 7-kW model 6237. Generac now have a newer model 6519. However, this size may not be sufficient if you have a central air conditioner. As a rule of thumb, an average house with 5-ton a/c typically needs a system rated 15-17kW or greater.
Here are some lesser known details that you need to know when you are selecting a natural gas generator for your home. A typical gas meter is rated to 250 CFH. This may not be enough if you are adding a large genset. An engine will not provide full power if it is not supplied with the fuel amount specified by its manufacturer. In this case, you will need to ask your utility company to upgrade your existing meter to a higher-volume one. Also, some older models may require the gas pressure to be greater than the standard delivery pressure available to your house. Be sure to check the model's requirements. The typical pressure in residential installations is 0.2-0.25 psi (5-7 inch water column). If you choose a device that requires greater psi, you may need to install a split-meter with two regulators. One will provide a higher pressure, and the other one will drop it to the normal level for the rest of your appliances. The above upgrades may cost anywhere from zero to $5,000.
A stationary NG system seems to be an ideal power backup for the whole house. Nevertheless, in an unlikely event of a major natural or other disaster the gas supply may be interrupted as well. In this case, you may switch to a propane tank if you have a bi-fuel system. If NG service does not exist in your neighborhood, you probably have a large propane tank that is periodically refilled by a local distributor. Propane
has practically unlimited shelf life and it is normally obtainable during power outages. In can be used in both fixed and portable devices. In my view it is the best choice
for portables. Of course, one 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. This makes them more appropriate for industrial applications. In addition to this, diesel, like gasoline, may not be available during a major blackout. For the current prices on some of the top rated residential models see our discount generators picks
Normally, a stationary genset is mounted outdoors on a cement pad. Preferably it is placed near the fuel source. Many models already come with a mounting pad. In any case, 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 (2015 Edition of NFPA® 37 requires at least 5 feet separation). Due to the heavy weight, you may want to request lift gate service when the freight company calls you to schedule the delivery. Otherwise, have at least four strong persons present to unload the device.
HOW TO WIRE YOUR SYSTEM.
A standby power backup device connects to the house wiring via a transfer system
, which is usually installed indoors. It prevents "backfeeding" into utility lines (which is dangerous and illegal). It also protects your device from damage by preventing utility 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 for home use come with an already pre-wired transfer switch.
Generac® whole house standby system
. This is how a typical model looks like.
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 and NFPA® 58 for liquid propane applications.
WHERE TO BUY.
Gensets are available direct from manufacturers, from authorized dealers, hardware stores, as well as online from independent retailers. Buying online has certain advantages, such as broader selection, lower prices, and possibly no sales tax in some states. Among reputable online 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. It usually offers free shipping on the gensets it carries. Alternatively, you may request a quote
from a local dealer. Note that with most manufacturers, you can usually order the installation and maintenance from their local service provider regardless of place of purchase, i.e. even if you bought it elsewhere. Of course, you can always hire your own contractor to do the installation.
Although a genset may be a relatively inexpensive way of supplying emergency power, it has certain disadvantages too. The main "cons" are noise, air pollutions and engine maintenance. If you prefer to use a silent, environmentally friendly and low-maintenance backup energy source, consider a battery-based system, such as solar-powered
Below you will find additional guides and reviews of residential gensets, safety recommendations and other facts you need to know. They will help you make an informed decision about the best emergency back up generator for your home.