The frequency of power outages in US and the number of people affected keep increasing. Since most electrical lines in US use overhead wires, and because of deteriorating infrastructure of our power grid, this trend will likely continue. This definitely justifies growing interest in backup generators for home use. Unfortunately, for most consumers who do not have a background in electrical engineering, choosing a backup system can be challenging. What type is best for power outages? Why would I pay $4,000 for a standby genset plus several more thousands for the installation when I can buy a portable one for under $400? These are the commonly asked questions. This guide is designed to provide you with practical facts and important information you need to know to buy the right generator for your home or business.
HOW THEY WORK.
To choose the right type of generator for your particular requirements you need to have at least some basic understanding of its operation. So, let’s first briefly review how generators work and what is common to all of them. Technically speaking, the operation of any electric generator is based on a physical phenomenon called electromagnetic induction. This phenomenon is that changing the magnetic field induces a voltage in a conductor placed in this field. Of course, creating and changing any physical field requires an external energy. In the generator it is provided by the fuel. When the supplied energy is consumed to create the variable magnetic field, it is converted to electrical energy. If the magnetic field is rotating with a constant speed, the induced voltage will be sinusoidal, which is what we need in our household. In the designs suitable for household use, the rotation is provided by a rotary engine that spins an electromagnet around copper coils. So, in practice, what we call a generator is actually a combination of the generator itself (also known as an alternator) and a device that rotates the magnetic field. In most models (except for PTO), these two parts are mounted together and form a so-called engine-generator set (or a genset). A genset is the most common type of a backup power source for the home. It runs on a fossil-based fuel, such as natural gas, propane or gasoline. The gensets suitable for homes are available in a wide range from 500 watt to tens of kilowatt, so you can always find the right size for your application. Cost-wise, you can get a portable model for about $100-200 per kilowatt, while complete stationary systems with auto start run for $400-600/kW installed. Note that because the engines produce toxic emissions, all gensets have to be run outdoors only.
TYPES OF RESIDENTIAL GENERATORS
During the infamous Northeast blackout of 2003, I heard from some people: We should have had a generator. They tend to think about it as if it was a kind of generic device that could provide electricity during an outage. But when they looked into various catalogs they got puzzled because they saw models ranging from $200 to $5000. Well, there is no such thing as “a” generator. There are various types of electric power generators. They are subject to a number of classifications, which may overlap. Most buyer guides tell you that there are two types- stationary and portable. In reality, there are more. Depending on the connection and activation methods there are five basic types of generators: permanent (standby), portable, trailer mount, PTO, and RV.
Standby devices are installed near your home and are hardwired to a transfer panel. The transfer panel in turn is permanently connected to both the house wiring and utility lines. The standby generator is also hooked up to a fuel source, such as a natural gas, propane or diesel. Because this requires professional installation, it will always take a certain amount of time until you can begin using such a system. However, once it is installed, a standby model can be activated immediately (either manually or automatically) and effortlessly. It can then provide power practically indefinitely for as long as there is a flow of fuel.
Portable devices are intended to be stored indoors or under a roof and connected only when you need them. In an emergency or when away from the grid, you need to move them to the place, fill with fuel, manually start up, and finally connect to your loads. Most portables are fueled from an on-board tank, which may need to be refilled as often as several times a day.
Trailer mount or towable generators have many of the features of stationary generators (such as automatic start with optional transfer switch) with added portability. They are often used as rental generators and can work in different commercial and industrial applications. Unlike other types, trailer mount models normally produce a variety of voltages. Besides 120/240 VAC single phase, they can usually provide three phase 208 VAC, 240 VAC, and 480 VAC. A rotary selector switch lets you choose a required voltage. This type is primarily for industrial buildings or large houses.
Power takeoff (PTO) generators are the only type that does not include an engine and therefore is not a genset. They use a tractor’s engine to drive the alternator. Today’s tractor PTO shafts spin at 540 or 1000 RPM. For 60 Hz output this rotation is converted to 1800 or 3600 RPM of the gearbox shaft depending on the number of alternator poles. Of course, you need a tractor to drive a PTO. Therefore, this type is suitable primarily for a farm or a ranch.
RV generators are designed for powering recreational vehicle appliances, primarily air conditioners. Unlike other types, these models are often powered from the RV main gas tank and normally have a remote start.
HOW TO CHOOSE.
For most urban homeowners the main options are either fixed generator or a portable one. When selecting the type, basically you need to make a choice between cost and convenience. A portable genset can be much cheaper, but you have to be prepared to roll a few hundred pound device and deal with a gasoline container, extension cords, and frequent maintenance. It you are a type of person who can maintain and operate a snow blower, a portable generator may be for you. However, if you prefer to go to a mechanic when you want to check engine oil level- stick with a fixed one, which is the easiest type to use. Once it’s installed, it can do everything for you by itself- sense power outage, automatically start, and then automatically shut down when grid is back on. You don’t have to rise from your coach and don’t even have to be home. However, of course, it costs more than portables and requires a costly installation of a transfer system and a fuel line.
The other important factor to consider is access to the fuel in an emergency. Obviously, all gensets can generate electricity only for as long they are supplied with fuel. If you have a continuous supply, such as a natural gas line, you can be getting emergency power practically indefinitely. That’s why stationary devices are the only type of system suitable for long-term blackouts. However, if you picked a portable model that runs on gasoline, you may end up without fuel in less than a day.