An Extensive Guide to Choosing the Perfect Portable Generator

With the important range of portable generators on the market, choosing an appropriate one could seem a daunting task.

Moreover, besides that important variety of products, numerous characteristics have to be considered in order to ensure that the unit of your choice fulfills your needs.

The following article serves as an introduction to portable generators and provides further tips for choosing the best model for you.

How to Choose the Best Portable Generator for You

The following is a list of exemplary scenarios most commonly encountered by portable generator users and the best possible solution to them.

What if you wish to produce electric power just occasionally, for example for tools or lighting, in a location which is out of the reach of a power grid?

The best choice in this case would be a gas-run portable generator (preferably 4-stroke), rated for roughly 3000 W, with an open frame and a classic recoil start. You needn’t worry about voltage regulation for the aforementioned appliances, as they are not generally considered sensitive equipment (if not stated otherwise by their manufacturer).

What if you wish to go camping or RVing, and wish to enjoy the comfort of a coffee maker, television, or to recharge your batteries (for your car, smartphone, tablet, etc.)?

In this case, a portable inverter generator with a 4-cycle engine is the way to go. A power output of roughly 2000 W can be expected by these devices, which is enough for occasional use and small devices. It should be noted that inverter generators are suitable for sensitive equipment, as they regulate the sine wave of the current and thus, protect your electronics from damage.

What if you’re a professional, who needs a portable generator for work in locations which cannot be powered by a mainline?

The answer is a generator with a power output of a minimum of 10 kW, which can provide both 120 and 240 V and thus, meets the power requirements of your equipment. An AVR (automatic voltage regulator) feature is desirable, as it helps maintain a stable and steady voltage, without extremities. The device should also provide GFCI outlets to ensure safe use and compliance with OSHA regulations.

What if you wish to purchase an emergency backup power source for your household, which will aid you in cases of frequent and long power outages or natural disasters?

4-stroke, gas-run devices should be your priority, with a rating of roughly 5000 W. Portable inverter generators of such ratings are somewhat rare, and thus, to prevent the damaging of your more sensitive electronics, as for example computers, seek a generator with a THD of less than 5%.

To seamlessly switch from the grid to your generator during an outage, choose a product which is transfer switch ready. For further safety, we recommend models featuring GFCI outlets and circuit breakers.

Portable Generators: An Overview

Picture of Michael Faraday

Michael Faraday discovered electromagnetic induction

Production of electric power has been known since the 19th century. The principle, based on the invention of Michael Faraday from 1831, is still currently in use. In simple terms, the easiest method of creating electric power is to perform rotary motion of an alternator and transform its mechanical energy to electrical energy.

Thus, all generators have an alternator, whose rotation is ensured by an engine.

An alternator has a characteristic power rating which it can generate. It may be expressed in W (watts) or VA (volt-amperes). For simplicity, we can approximate that 1 W = 1 VA, while more accurately 1 VA is roughly 0.8 W. The voltage of an alternator can be 120, or also both 120 and 240 V.

Most contemporary generators feature multiple security features and regulatory systems, which guarantee a stable power output and a swift and reliable defect detection (such as thermal, magnetic, or differential protection).

An engine of a portable generator may run on gas, propane, diesel, solar energy, or in some cases, a combination of them (though most commonly, dual fuel generators run on gasoline and propane).

A generator’s engine’s power (in terms of displacement or horsepower) determines its ability to rotate alternators of different dimensions and thus, is directly linked to the power output of a generator. We shall focus on gasoline and propane-powered generators. They’re the simplest and most reliable, since if you have fuel, you have electricity.

A portable generator can weigh anywhere between 20 and 400 pounds, sometimes even more. Its weight is mostly dependent on the power it can generate. The name portable just indicates that they differ in design from stand-by generators. While they technically may be moved, they are not always easily carried.

Even though most portable generators can be lifted (especially inverters), a wheel kit or a lifting eye may be included to ease the manipulation and loading of some of the heavier models.

As is the case with any engine, even a generator’s engine must be maintained regularly to ensure its proper function. To keep your generator in a good condition, it must be looked after well. To further lengthen its lifespan, it is recommended to avoid using it at a full load on a regular basis (optimally, a 75-80% load should be maintained).

For more information regarding all the parts of a generator, check out our Anatomy of a Generator article.

The Different Types of Portable Generators

All generators utilize the same mechanics. However, they do not all use the same technology and in general, offer different features on a model by model basis.

There are 3 groups of portable generators:

  • Gasoline-powered generators
  • Propane-powered generators
  • Dual fuel generators

Gasoline-Powered Generators

portable generator 5 gallon fuel tank

A standard 5 gallon gas tank, found on many open frame portable generators

Gas-run portable generators are the most common design and easily fit any circumstances, be it household or DIY use, outdoor hobbies, such as tailgating, camping, or even professional activities.

They may be started via a pull-start mechanism, electric starter and some even remotely. The power of a gasoline generator can reach anywhere between 1 kW and 15 kW, based on their size.

Generators with 4-stroke engines (which are an overwhelming majority of them) are easily refilled with unleaded gasoline (check their user manual for specific information) and do not require you to mix their fuel with oil.

The rare 2-stroke engine generators will require you to premix the fuel with oil before filling them. While the fuel/oil ratio is most often 50:1, it can vary by unit. It is therefore recommended to check the owner’s manual for a recommended fuel/oil ratio.

Propane-Powered Generators

picture of a 20 lbs propane tank

The 20 lbs propane tank serves as reference for runtime on propane

Only a few portable generators run exclusively on propane. Propane-powered generators have some advantages over gasoline-powered ones.

  • They are a more environmentally friendly alternative, as propane burns in a cleaner way than gasoline.
  • Unlike gasoline, which can degrade over time (due to the separation of its components), propane does not go off and has an infinite shelf life. Therefore, when natural disasters occur and gas pumps are unavailable, you can still run propane generators from your own stock.

However, they have a couple of disadvantages:

  • Their fuel system is more complicated, has a higher risk of malfunctioning and can be difficult to fix.
  • They don’t run well at low temperatures.

To get the best of both worlds, you can opt for a dual fuel portable generator, as it will allow you to choose which fuel to burn according to your circumstances and needs.

Dual Fuel Generators

Picture of the Firman H05753 Dual Fuel Portable Generator

Firman Power Equipment has a good range of dual fuel portable generators

Dual fuel generators are the most versatile choice, as they give you the advantages of both types of fuel.

Most dual fuel models also exist in a single fuel (gasoline) version and are usually differentiated by a slight difference in their model number. For example, the DuroMax XP10000EH is dual fuel, whereas the DuroMax XP10000E only runs on gasoline.

All dual fuel generators feature a switch allowing you to choose which fuel to burn. However, the technology in use can vary. Some units may allow to instantly switch from one fuel to another, whereas other units may require you to shut off the generator before changing its fuel source.

Standards & Compliance of Portable Generators

Whichever type or model of a generator you’re considering buying, you should check if it complies with your local or professional laws and standards. Here are a few certifications and standards that may apply to portable generators:

epa label

EPA: Stands for Environmental Protection Agency. It means that the emissions of common pollutants such as carbon monoxide (CO), sulfur dioxide (SO2), particulate matter (PM-10 and PM-2.5), nitrogen oxides (NOx) and volatile organic compounds (VOCs) were controlled.

carb label

CARB: Stands for California Air Resources Board. This certification is mandatory for residents of California. CARB compliance indicates the same thing as EPA, but the tests done on emissions follow much stricter guidelines.

csa label

CSA: Stands for Canadian Standards Association. The certification ensures protection against fire hazard, mechanical hazard, and shock or energy hazard. It is mandatory for any electrical product installed in Canada. Doesn’t apply in the USA.

ul label

UL: Stands for Underwriter Laboratories, an independent security consulting company. This certification label guarantees that a product complies with security and quality norms in the US and in Canada.

osha logo

OSHA: Stands for Occupational Safety and Health Administration. This standard applies mostly for professionals and covers grounding requirements for portable generators. In a nutshell, a generator must have GFCI (Ground Fault Circuit Interrupt) outlets to be OSHA compliant.

Main Specs of Portable Generators

Before choosing the right portable generator for you, it is crucial to identify your power requirements. Going too small will result in the generator quickly wearing out and frequently failing. Vice versa, go too large and your generator’s capacity will be wasted, which may result in leakages or malfunction.

It is therefore necessary to pick the right generator type and model to fulfill your needs.

The following aspects should be considered when choosing your portable generator.

Power

Power is by far the most important spec of a portable generator. By power, we understand the power output of the device, not the power of its engine. To estimate the size of your generator, you have the following choices.

wattage table

Make a list of your appliances and their power consumption (source: Yamaha Motor)

The first choice is to list all your appliances, tools and accessories, which are to be plugged and powered via your portable generator and write down their respective power consumptions (note the rated and the surge power separately).

Their rated wattage should be added, and the total multiplied by 1.25, since as we have previously stated, running the generator at 80% of its power helps maintain its lifespan and leaves some leeway. The result is the recommended rated wattage of your generator.

In the case that you are unsure which devices will be powered by your generator, keep in mind that all devices with an electric engine will require an extra wattage spike to get started – make sure to add it (note the rated and the surge power separately).

Voltage must also be considered. In the USA, most devices run on 120 V. However, many tools and household devices (e.g. electric ranges) need a voltage of 240 V. In case you require powering these devices, you must make sure that your generator has a 240 V output voltage.

The second choice would be to use our wattage calculator as a guideline to determine an appropriate size for your portable generator.

Engine

The overwhelming majority of portable generators run on a 4-cycle engine. Here are a couple of engine specifications which should be taken into consideration:

honda gx340 engine

The GX340, an OHV engine powering some Honda generators

While there are several exceptions, almost all portable generators are powered by a 4-stroke OHV engine. Such engines have the advantage of being less bulky and having a simpler drive and lubrication system than other engines.

Some of the most powerful portable generators feature a V-Twin engine. These engines can rotate at a higher speed, and, for their power are lighter and better balanced than others.

The engine displacement (cc) has an indirect impact on the power that the generator can deliver. A higher cc is accompanied by a higher weight, but not necessarily a higher output, as that also depends on the alternator (the higher the cc, the bigger the alternator which the engine can rotate).

Starting System

The choice of a starting mechanism is most crucial when dealing with generators with an output of 3000 W and lower. Even though most models have a recoil start, some feature an electric start. The difference boils down to how many pulls you can put up with when starting your generator.

For occasional use, a classic pull-start mechanism is the way to go. However, for daily use, it is preferable to invest into an electric start (additional maintenance is required for the starter’s battery).

Almost all portable generators featuring an electric starter also have a backup recoil start. Many advanced models with an electric starter can even be started remotely (using a key fob).

The Different Types of Voltage Regulation

We arrive at the complex topic of the creation of an electric current. This applies especially if we desire a stable current (and frequency) from a rotating device, which is by principle, unstable (the engine). However, electronics can be used to fix that.

For portable generators, 2 major types of voltage regulators arise as a viable option.

Generators with Automatic Voltage Regulation (AVR)

AVR stands for Automatic Voltage Regulation. Basically, the technology utilizes an array of sensors for the monitoring of the engine’s speed and to ensure the stability of the generator’s voltage.

Inverter Generators

Energizer eZV2000P inverter generator

The somewhat standard design of a portable inverter generator. Picture: Energizer eZV2000P

The inverter technology is currently considered the best for voltage regulation. Electronic components utilize the alternator’s tension and recreate it. The current, created by the inverter, is thus perfect enough to be considered a clean sine wave, with a THD below 5% and quite commonly even below 3%.

The inverter technology is the best solution for powering sensitive electronics, such as mobile devices or personal computers. It is also interfaced with the injection mechanism of the engine, allowing it to reduce the engine’s speed (along with its fuel consumption), during lower loads.

Further Generator Specs

Apart from the power, regulation and fuel types, we shall provide several other specifications for your consideration.

Weight: How Much of a Nomad are You?

In summary, the higher the power, the bigger and heavier the engine will be.

DuroMax XP15000EH being lifted

The XP15000EH is powerful, but weighs close to 350 lbs

If you intend to regularly change the location of your power generator, you should take its weight into consideration. Portable inverter generators are usually the easiest type to carry around and are well adapted to a nomadic lifestyle. However, even though powerful ones exist, if you want to keep the weight below 80 lbs, you won’t find any whose power output exceeds 3500 W.

If mobility is not your priority, you should consider a traditional open frame generator with a wheel kit.

Here are a few examples to give you an idea of what weight ranges you should expect based on the generator’s power:

  • Under 2 kW: 20.3 to 91 lbs
  • 2 kW to 4 kW: 48 to 204 lbs
  • 4 kW to 6 kW: 99.5 to 261 lbs
  • 6 kW to 8 kW: 140 to 260 lbs
  • 8 kW to 10 kW: 185 to 403 lbs
  • Over 10 kW: 218 to 392 lbs

Noise level: Will It Disturb You or Others?

When it comes to noise emissions/pollution, inverter generators are by far the quietest type.

a woman putting a finger in front of her lipsYou should keep in mind that there is no industry standard for the measurement of the noise produced by generators.

The unofficial standard is to measure the sound level at a distance of 23 feet, but manufacturers are actually pretty much free to state whatever noise level they see fit: the tests could be done at different load levels (under no load, at 25% load), with or without a muffler, behind walls, etc.

The stated noise values should therefore be taken with a grain of salt, as testing conditions could be tweaked to serve marketing purposes. The lack of standardization even leads some manufacturers to simply omit the noise rating all together.

Here are a few examples to give you an idea of what is the minimum noise you should expect based on the generator’s power:

  • Under 2 kW: 42 to 95 dBA
  • 2 kW to 4 kW: 50 to 76 dBA
  • 4 kW to 6 kW: 52 to 86 dBA
  • 6 kW to 8 kW: 59 to 86 dBA
  • 8 kW to 10 kW: 69 to 80 dBA
  • Over 10 kW: 69 to 85 dBA

Runtime: Fancy Waking Up for a Refill?

an alarm clock without batteriesUnless you want to keep refilling your unit all the time, runtime, capacity of its fuel tank and fuel consumption of your portable generator should be thoroughly considered.

Generator runtimes fall anywhere between 4 and 16 hours+. Your choice should reflect your personal requirements.

For example, when in an RV – To enjoy the comfort of your AC throughout the night, you should opt for a generator that can run for at least 8 hours at a time.

Outlets: What Tools and Appliances Will You Run?

All portable generators sold in the US will provide you a standard NEMA 5-20R 120 V household outlet.

However, some tools and appliances may require other types of outlets. If you don’t want to deal with a bunch of adapters, try planning ahead and check out the NEMA standard for the appliances you wish to power by your unit.

The most popular types of outlets include NEMA 5-20R, L5-30R, TT-30R, L14-30R, and 14-50R.

Security Features

electric hazard signMost of the portable generators offer various security features, including low oil alert/shutdown and overload protection.

The low oil alert works thanks to a sensor that simply measures the amount of oil inside the engine. When the oil level is too low, the generator will trigger a warning light indicator and/or automatically shut off the engine.

Overload protection takes the form of circuit breakers that will automatically trip if you’re asking too much of your generator. Remember to NEVER overload your generator, as in addition to the risk of possible internal damage and fire hazard, you could also damage any plugged appliances.

Generators CANNOT go over their rated (running) wattage. The only exception is the starting wattage. Circuit breakers allow a surge (starting) wattage to pass through, but only for the few seconds needed to start an engine.

These security features exist to protect the generator, but also the appliances plugged into it and, most importantly, human lives.

7 Key Points for Choosing A Portable Generator

In summary, you should choose a portable generator based on its features, which should satisfy your personal requirements.

  1. Imagine the occasions, during which you will need your generator (home, work, camping, etc.), to help you consider the required mobility and noise rating.
  2. For a home backup power supply, we recommend a generator with a THD below 5%, to ensure the safety of your sensitive electronics.
  3. Create a list of the devices which you wish to power and consider their wattages to evaluate your power requirements.
  4. Electric starters are preferable for regular users as they offer comfort over a recoil pull-start.
  5. Consider runtimes based on how often you’re comfortable with refilling the fuel tank.
  6. Check your appliances for required voltage (120/240 V).
  7. Utilize the parallel capability, which will allow you to simply plug in an extra generator whenever you wish to increase the power output.

Using and Taking Care of Your Portable Generator

  • Electricity is a health hazard and any electric components and devices should be handled with care. Pay attention to the plugged devices, plugs, contact with water (especially on work sites) and to the condition of power cables. Do not hesitate to fix any problems as soon as they arise, and don’t forget to turn off the power supply before doing so.
  • To ensure a maximum lifespan of your portable generator, keep to the maintenance schedule as it is stated in the owner’s manual. Fluids and filters must be changed on a regular basis. Any moving parts must be greased when required. It is also recommended to measure the generator’s power output occasionally, which may help indicate a fault.
  • Portable generators should be stored in a stable, clean and dry environment, both during and after use.
  • When staying in proximity of a generator, consider using hearing protection. However, for your comfort, it is always preferable to keep your generator out of reach, regardless of its noise rating.
  • If on a construction site, pay attention to the movements of construction vehicles and machines. Your portable generator must be indicated and easily spotted. In addition, any power cables must be kept out of frequented pathways to prevent damage.
Paul

Paul

Founder of generatorbible.com. Early retired from the OPE industry, living in South Carolina. He now mostly spends his time traveling and taking care of his wife and grand-children.

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