How to Select the Right Generator for Your Needs
Power outages can happen anytime, and the duration may be minutes, days or much longer. As it is their business to supply power to consumers, utility companies are quick to respond in most cases – but as millions of customers in California’s more rural areas have discovered, power companies will intentionally shut off the flow of electricity for days at a time in the name of public safety.
“Putting budget aside, the first consideration is what you intend to power. The more devices, or the higher the current requirement for the most power-hungry appliance you need to run, the higher the output capacity of the generator must be.”
Utility companies recommend personal power generation as a critical part of a preparedness plan, and this is especially crucial for families that include someone with medical issues that depend on devices reliant on electrical energy – be it an electrically powered oxygen concentrator or a refrigerator for insulin.
Large standby generators are employed by hospitals, municipal buildings, public safety departments, as well as many businesses and homes to cope with power outages. These permanently installed generators are driven by internal combustion engines that run on diesel fuel, natural gas or liquefied propane (LP/LPG), and the power generator system is sized to meet the demand of the facility which it powers.
On the other hand, most portable generators on the consumer market run on gasoline; but just like the big standby generators that automatically start up and kick in when grid power is lost, portable generators must be sized to meet the load they are intended to power – be it just an essential appliance plus a few lights, or an entire home including the HVAC system, electric range, water heater and dishwasher. There is no one-size-fits-all solution, and the price range for portable generators runs from a few hundred dollars to several thousand. Choosing the right portable generator for your needs requires a good deal of consideration, some calculation, and a bit of speculation.
Putting budget aside, the first consideration is what you intend to power. The more devices, or the higher the current requirement for the most power-hungry appliance you need to run, the higher the output capacity of the generator must be. Also, appliances such as electric clothes dryers and central air conditioning compressors (the part outside of your house) usually require 220-240 volts alternating current (AC) to operate, so the generator must be able to supply the proper voltage in order to run those devices; not all portable generators have this capability.
Another issue to consider is your portability requirement. If the generator will be moved from place to place around the home or property, wheels make that process easy; transporting a generator over longer distances means lifting it into the back of a truck or onto a trailer. High-output generators (10,000 watts and up) can weigh in excess of 200 pounds, making them difficult to load even if an extra set of hands is available. These heavy generators often have lifting eyes on top, allowing them to be loaded with the help of a winch and an overhead support such as a stout tree branch.
Fuel storage is another consideration. In a long-lasting power outage, fuel may become scarce, so you could find your power production capability limited by what fuel you have on hand. Gasoline, if stored improperly, will start going bad in as little as a few weeks but could last six months or more under the right circumstances. However, if it is properly stored and treated with a stabilizing additive, it can be good for a year or longer. Rotating fuel out of storage and into your vehicle’s gas tank will ensure fresher gasoline is available for your generator when needed. Unless you are expecting to need to run the generator within the next few days, or you test it regularly, it is best not to fill the tank; fuel remaining in the tank, fuel lines and the carburetor will go stale and gum up the components, which can put your generator out of service.
To figure out how much load you plan to power, go through your home and add up all the devices you wish to use: water heater, central heating and cooling, electric stove, microwave, light bulbs, security system, etc. Write down what their current draw is (in amps), or specified wattage, according to the labeling on them. While this may seem rather straightforward, it can get a bit complicated.
Generator output is normally stated in watts, and many electrically powered devices have their wattage specification clearly marked on their packaging or label, but some only display amperage; to determine how many watts an appliance or other device uses, multiply the amps by the voltage, as listed on the label. For example, if a product uses 5 amps at 120 volts, you multiply 5 by 120 to find it consumes 600 watts. Powering three such devices at the same time would consume 1,800 watts, or 1.8 kilowatts (kW) – a relatively inexpensive 2,000-watt (2kW) generator would handle such a load with ease – but it isn’t always that simple. The type of load connected to the generator must also be taken into account. Purely resistive loads, like the elements in an electric water heater, are a constant load that is either on or off, whereas the compressor motor in your central air conditioner and the blower motor that moves the air through your vents are inductive loads. They may draw 10 amps when running but require two or three times that to start up; they require this extra surge of power for only a few seconds as they come up to speed, but the generator must be able to meet this demand in addition to the normal running watt load.
If you don’t enjoy math, you can always use one of the many online calculators or tables that list the average power requirements of typical appliances. Just be sure to add a little extra overhead for things you may have forgotten to include … such as your neighbor’s electric lawn mower.
“Utility companies recommend personal power generation as a critical part of a preparedness plan, and this is especially crucial for families that include someone with medical issues that depend on devices reliant on electrical energy…”
Now that the power requirement in watts is known, you can find a suitable generator to meet that demand. The watt rating on any particular generator will be stated in two different numbers: 1, the running watt rating – the maximum power output it can sustain indefinitely; and 2, the starting (or surge) watts rating – the amount it can supply for short periods of time without stalling or suffering damage.
Powering your whole house with a portable generator is possible and practical.
Depending on the size and location of your home and the level of comfort you wish to maintain, a generator of 10,000 to 15,000 running watts will probably be adequate.
Connecting a generator to the home’s wiring comes with an added concern – keeping your generator from back-feeding into the utility lines. Any electricity you may inadvertently put back into the lines poses an extreme hazard to linemen who may be working to restore power. Installation of a transfer switch between your power meter and your breaker box allows you to safely switch from utility power to generator while preventing electricity from flowing back out through the lines. It also keeps utility power from coming straight into your generator when grid power is restored.
“Depending on the size and location of your home and the level of comfort you wish to maintain, a generator of 10,000 to 15,000 watts will probably be adequate.”
If you are powering only essential devices, quality extension cords are certainly an option. Portable generators typically have multiple 120-volt outlets, and those that provide 240 volts will sometimes come with a heavy extension cord that splits into multiple 120-volt outlets, allowing you to power several 120-volt devices from the single 240-volt outlet.
Never, under any circumstances, run a portable generator inside your home or in any enclosed space. The exhaust from the engine contains carbon monoxide – a deadly byproduct from the combustion of fuel. When you’re running one outdoors, be sure the exhaust cannot enter the dwelling through any windows, doors or fresh-air intakes.
Until fairly recently, portable generators were notoriously noisy contraptions, but advances in inverter generators have changed that characteristic drastically. While the larger, higher output-capable traditional portable generators have to run at a constant speed to produce a clean alternating current at the desired frequency (60 hertz in the United States), inverter generators produce a pure AC sine wave through electronics. The principal of generating the electricity in an inverter generator is the same – spinning an alternator – but the AC is first converted to direct current, or DC, and then transformed back into alternating current at precisely 60 hertz. The engine has to run only as fast as necessary to meet the power requirement of the attached load; when the load is light, such as when running a few light bulbs, the engine runs at a low rpm. As the load increases, such as when higher current is demanded for starting the compressor on a refrigerator or air conditioner, the engine revs up to provide more power, and then slows back down to match the lower running load of the appliance. Not only are inverter generators much quieter, they can be significantly more fuel-efficient.
Physically smaller and lighter in weight than traditional generators, inverter generators are usually rated toward the lower end of the power spectrum. At the time of writing, the largest commonly available inverter generator maxes out at 7,000 watts surge capacity, 5,500 watts continuous. However, many inverter generators can do something their larger cousins cannot do – run in parallel. Since the output is controlled electronically, the output of one is synchronized with that of the other, making it possible to connect two compatible inverter generators together to produce twice the power. Of course it costs twice as much plus the cost of the optional parallel kit, but it is a feature that puts miniature powerhouses back in the big league. While the cost of an inverter generator is considerably higher than that of a traditional generator of the same output capacity, the benefits of being super compact, quieter running, offering higher fuel efficiency and superbly stable power output justifies the price for many.
A growing trend in portable generators is multi-fuel capability. While adapter kits have long been available to run gasoline engines on propane, many manufacturers make generators that have the capability to run on gasoline or propane with no modification required. Propane is not only safer to store, as there is less chance of spilling the sealed, pressurized bottle, it also has a much longer shelf life, possibly 30 years or more. While the power produced by a gallon of propane is a bit less compared to a gallon of gasoline, the lower cost of propane in most areas can make it more economical; but even if the costs were the same, having the ability to run your generator on fuel that will likely be readily available even during widespread power outages is very much a good idea.
“Until fairly recently, portable generators were notoriously noisy contraptions, but advances in inverter generators have changed that characteristic drastically.”
Diesel engines are the predominant choice for large standby emergency generators, but their use in portable generators is rather limited. Few manufacturers make diesel engines small enough to be used in portable applications. Diesel does have some significant advantages over gasoline – it can last longer in storage untreated, and it is much safer in the event of a spill, as it lacks the volatility and explosive vapors of gasoline.
Portable generators do have a place in a preparedness plan, and like anything else your safety and security may rely on, it is not a place to skimp on quality. Before investing in a generator, consider how you plan to use it and where you will store it and the fuel it requires, calculate the minimum electrical demand it must meet, and speculate on how changes in your situation might affect the choice you make.
Typical power requirements
|Device or Appliance||Running Watts
|60-watt incandescent bulb||60||60|
|1,600-watt radiant heater||1,600||1,600|
|Refrigerator or freezer||200||1,200|
|¼-horsepower furnace motor||600||1,000|
|Electric clothes dryer (240 volt)||5,400||6,800|
|Well pump (1/3 HP)||800||1,300|
Briggs & Stratton portable generators
Briggs & Stratton Corporation
Champion portable generators
Champion Power Equipment
Generac portable generators
Generac Power Systems, Inc.
American Honda Power Equipment Division
Westinghouse Outdoor Power
Propane and natural gas adapter kits
Editor’s note: A version of this article first appeared in the March, 2020 print issue of American Survival Guide.