HOME GENERATORS BASICS

WHAT IS IT?

The term generator casually refers to a fuel-powered device that can supply electricity to your house during power outages. During an emergency, it can allow you to continue using essential appliances and lights. If it's properly designed, it may even power an entire house. Let me first explain basic generator operation really quick. This may help you better understand the differences between different types. The following definition may sound surprising, but technically speaking, an electric generator is a device that converts mechanical energy into electric energy. Now, where does this mechanical energy come from, you may ask? In general, there are of course various ways of producing it depending on the application. In the generators intended for home use the mechanical energy is produced by small engines. Basically, the way it works is the spinning shaft of the engine creates an alternating magnetic field through a coil, which induces voltage. So, when we buy what we call a "generator", we actually get an appliance that includes an engine and an generator mounted together. That's why a more technical term for this device is an engine-generator set or genset. Since there are different types of the engines, the properties of gensets are likewise functions primarily of the type of their engine, which we will discuss below.

HOW TO CHOOSE A GENERATOR.

Let's quickly go over the different types that are out there. Depending on the way they are connected and activated, generators can be stationary (standby) or portable. Depending on design, their engines can 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 the cheapest ones. For example, you can buy a 4000W set for about $300-400. However, firstly, 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. As you may recall, in Florida most gas stations already run dry a few days before hurricane Irma hit the coastal area. After North American winter storm Uri of February 2021, gas stations in the affected areas did not work until the power was restored. Even then, the fuel deliveries were delayed because of icy roads. That's why for a long-term emergency you should consider standby sets. They can provide continuous power because they are hooked up to an external fuel source, such as natural gas (NG) line. That said, 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 permanently connected to both the house wiring and the fuel source. 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 from the grid your electrical wiring or designated emergency circuits, 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. Therefore, if you run important computer applications, you may still want to have an additional UPS for power backup. It can prevent data loss during the transfer time. Note that even though natural gas powered gensets can provide practically unlimited run time (for as long as you have the fuel flow of course), you still need to periodically shut them down to change the motor oil. Depending on the engine specification, you may 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 systems generally offer power levels higher than portables. Their rating ranges anywhere from 5 kilowatt up into hundreds of kW. Such systems usually also increase the value of the house. All this makes them the best type of generators suitable for powering entire home, especially in case of the long-lasting power outages. Of course, they are more expensive and require professional installation, which are their main disadvantages. If you are looking for 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? Of course, you start your selection with wattage and cost. Besides this, 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 obviously is determined by the source you already use for the heating or by the fuels available in your area. Note that many permanent generators are bi-fuel. They can run on both natural gas and LPG (casually called propane). You may need just a simple adjustment to convert from one type to the other.
If like most homes your house is already supplied with natural 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 the best systems. Among major brands, the Generac's Guardian® models seem to have one of the lowest cost per kW. Given their 5-year warranty and a reasonable cost, in my view, they are the best buys. You just need to pick the right size. As a rule of thumb, an average house with up to 5-ton a/c typically needs a system rated around 15-18 kW. A good lower cost alternative to Generac is Champion's line. A consumer magazine's recent pick was Champion's 8.5-kW system, such as 100177. This particular model is on low end of power range though, but they offer systems up to 14kW.

Here are some lesser known details that you must know when you are selecting a natural gas generator. To install such a model, your home service should match its fuel rate and pressure requirements. A typical residential 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. If your system needs more fuel than your service can provide, you would need to ask your utility company to upgrade your existing meter to a higher-volume one. Also, some older genset models may require the gas pressure to be greater than the standard delivery pressure available to your house. So, 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. Don't be surprised, but the above upgrades may cost anywhere from zero to $5,000.

A stationary NG system seems to be an ideal for whole house power backup. Nevertheless, in an unlikely event of a major natural or other disaster the natural gas supply may be interrupted as well. You may recall, during winter storm Uri in Texas some natural gas lines were frozen. To prepare for such an event you may want to install a large propane (LPG) tank. It can be periodically refilled by a local distributor. With a bi-fuel system you would be able then to switch to LPG, which is your main option anyway if NG service does not exist in your neighborhood. Propane has practically unlimited shelf life. It is normally obtainable during power outages unless the roads are closed due to snow or ice. In can be used in both fixed and portable devices. By the way, in my view, propane is also the best choice for the portables. Of course, 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. This makes them more appropriate for industrial applications. In addition to this, diesel, like gasoline, may not be available during a major blackout.

INSTALLATION TIPS.

A stationary genset must be mounted outdoors on a cement pad. Preferably it is placed near your fuel source. Many models intended for home use 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 (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.

I'll go over this subject really quick. A standby device connects to the house wiring via a transfer system, which is installed indoors. It prevents so-called "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 the generator is running. In any case, without a transfer switch your device will likely be overloaded or damaged by the loads of neighboring houses that are served by the same line transformer. Some systems come with an already pre-wired transfer switch.
It is strongly recommended that all electrical connections be done by a licensed electrician. Depending on your local regulations, most likely you may be required to get the installation approval by your electric utility. You may need their certificate of compliance if later you sell your house. If you are going to store a large fuel tank, you likewise 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 free delivery. Among reputable online places to buy at a discount I would consider this one. It has the wide selection of Generac GUARDIAN®, Briggs & Stratton and other top ranking brands. And you can get free shipping on the gensets they carry. Note that with most manufacturers, you can usually order the installation and maintenance from their local authorized service provider regardless of the place of purchase, i.e. they would install and service it even if you bought it elsewhere. Of course, you can always hire your own contractor to do the installation and service.

By buying online you usually save money. The main disadvantage is, if the device arrived defective you would need to deal on your own with the repair or shipping it back. This may not be a trivial task. If you deal with a contractor who will handle both the delivery and installation, it would be his responsibility to get the system worked. If you choose this option, you may want to contact this referral service for a free quote. 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 required engine maintenance. If you prefer to use a silent, environmentally friendly and low-maintenance backup energy source, consider a battery-based system, such as a solar-powered one.





Below you will find additional guides and reviews of residential gensets, safety recommendations and other good to know facts. They may help you make an informed decision about selecting the right generator.

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