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Choosing A Portable Generator – What Features Should You Look For?

4 June 2011 4,669 views One Comment


You should choose a portable generator that best meets your power needs. Find out what features are the most important before you go shopping.

woman-turning-power-switch-on

You'll be able to turn the lights back on with your portable generator.

You don’t realize how much you depend on energy until you go without it for an extended period of time. No lights, no way to cook unless you have gas (or a fire), food spoiling in the freezer, no television, no hot water, and no heat or air conditioning, which in some cases can be life threatening. Most folks can generally get by for a few hours or a day like this.

I know growing up in the South of the US, we would have snow and ice storms in the winter and electrical storms in the summer that would knock down power lines and the power would be out for two or three days at most. It was pretty horrible. I can’t imagine what some people go through when the power is out even longer than that, after some disaster hits. You can’t stop Mother Nature, but you can be prepared.

If you don’t want to suffer through an extended power outage or even if you don’t want your food to spoil in the fridge after the power gets knocked out for a day or so, then you need to get a portable generator for your home. If you’re out shopping now, then you’re smart and thinking and planning ahead. Trust me, it’s better to be safe than sorry.

Of course there are other uses for portable generators. They can not only serve as a backup when the power goes out at your house, but you can also take them on a camping trip or for some fun tailgating. Most portable generators designed for camping are very quiet and can be used to power mini refrigerators and other kitchen appliances like blenders. They are also very useful on construction sites that have no electrical service. In this case generators can be used to run saws, drills, and other power tools.

Here’s what you need to look for when shopping for a portable generator.


Figure Out How Much Power You’re Going To Need

The first thing that you need to calculate is how much wattage you’ll need in your portable generator. Look at what you want to power up in your home in case of a blackout or what tools and appliances you’ll be using if you’re going to be on a construction site or out camping.

There are a lot of guides, calculators and charts out there that I found in my research that will help you calculate the wattage of a variety of common appliances. You can use this Generator Wattage Worksheet to help you in your calculations. Consumer Reports also has a wattage calculator as does the generator manufacturer Generac Power Systems. The chart below lists some other basic wattages of a variety of different home items. You can use this chart, but to get a more exact measure you’ll need to look in the Owner’s Manual of each appliance you own. Some may also have an electrical data plate on the motor that lists the power requirements for that device.

If amperage is listed instead of wattage then simply multiply amps times volts to get wattage. This article talks about the difference between amps, volts, and watts so that you can get a better understanding of these terms. If you want to be really exact you can use an electric usage monitor. These run about $25 and accurately measure wattage for any device that plugs into the wall and uses electrical power. You just plug the device into the wall socket and then plug the appliance into the device. These pretty cool and are also great ways to identify power hog devices in your home that you may not have even known were costing you so much.

Device Running Watts Required (average)
Central air conditioning (Average sized unit for a 2,200 sq/ft home) 10,000
Electric Welder (230 Amp AC at 100 Amp) 7,800
Electric clothes dryer 4,800
Water heater 3,000
Electric range (1, 8 inch element) 2,100
Table Saw (10 inches) 1,800
Microwave 1,500
Electric skillet (for camping) 1,500
Toaster 1,500
Window air conditioner (10,000 BTU) 1,500
Portable heater 1,300
Hair dryer 1,200
Coffee maker 1,000
Well pump (1/2 hp) 1,000
Desktop computer plus monitor 850
Sump pump (1/3 hp) 800
Ceiling fan 800
Dishwasher 700
Refrigerator 600
Fax 600
Furnace fan (1/4 hp, gas or oil) 600
Freezer 500
Lights (4, 100 watts bulbs) 400
Washing machine 400
Television 350
Laptop computer 250
Fan 200
Radio 100


After you’ve determined everything you’ll need to power up, add up all of the running wattages. Then you’ll need to add in the startup wattage of the item with the largest motor, like your refrigerator or freezer. When you first start a motor, or when it clicks on automatically, the wattage is 2 to 4 times greater than when it’s running at a steady state. For example a 1/8 horsepower electric motor connected to a fan on say your refrigerator may need 300 watts to keep it running. However to get the engine started it may need 900 watts. So if any of these types of devices, like a window air conditioner, automatically kicks on while you are running your generator then you need to be prepared for that. You can get a rough estimate of the surge or starting wattage by multiplying the running wattage by three.

The total of all of the running wattages of each item and the startup wattage of the largest motor is the wattage capacity of the generator you should be targeting. You don’t need to add in the starting wattage for each item because it’s unlikely that any two items would start at the exact same time.

Keep in mind it’s always better to go a little bit bigger than what you think you’ll need. In order to protect their internal wiring and prevent an overload, circuit breakers on most generators will shut off before the maximum load is reached. So add in another 20% to the total. That way everything will have enough power and your generator will operate efficiently. Experts also recommend running generators at 75 to 80 percent of their maximum wattage rather than full out because they will last longer.




Your Power Needs Determine The Size of the Generator

Generators fit roughly into small, medium, and large wattage categories and sizes. A small or medium sized portable generator will generally get the job done for you powering some basic household plug-in appliances. You can use these types of generators by simply running extension cords from the generator to the items you want to power. You need to make sure the generator is running outside. Most experts say it should be at least 15 feet away from your home to prevent any risk of carbon monoxide poisoning.

To run some of the larger items that are hardwired to your home power grid, like the furnace or heat pump and wall outlets, you’ll need a larger generator and a transfer switch. A transfer switch can be permanently attached to your electrical box by a certified electrician. After it’s hooked up, there’ll be just one plug and one cord going from the generator to the transfer switch. With this setup you don’t have to worry about running a bunch of extension cords in and out of your home from the generator to each appliance you want to run.

You can get either manual or automatic transfer switches. With the manual switch you need to go out and turn on the generator when the power goes out. The automatic kicks in on its own during a blackout even if your not home. Automatic switches will also perform self tests periodically and start the generator up to make sure it’ll be ready to go during an emergency. Manual switches cost around $500 including installation and automatic switches run about $1,000.


Small Portable Generator (1,000 to 4,000 watts)

Generators this size will get you up and running in case of an emergency and are great to use out on the trail. You can also install them on your RV, or truck camper. You can expect a compact recreational generator to produce about 1,000 watts of power which is enough to power one or two appliances at the same time. As you move up in wattage you’ll be able to power the basics in your home such as a refrigerator, a microwave, TV, several lamps, and a sump pump. You’ll be able to find many small portable generators priced from $500 to $800.

Most RV (recreational vehicle) generators will fit into the small portable generator category. Many of these types of generators can be mounted onto your truck or RV for convenient use out on the road or in a national park. There are a bunch of online forums that talk about using and installing RV generators. Check out RV.net to find out more.


Medium Sized Portable (4,500 to 8,000 watts)

You can power everything that the small size powers with the medium size plus a portable heater or a window air conditioner unit depending on the season. You can also add in a computer using an inverter generator to keep it from being damaged. I talk about inverter generators more below. If you want to substitute something you can get your coffee maker running as well. You’ll also be able to turn on a few more lights. If you are using a transfer switch with this size generator you can also use your water pump and furnace. Medium sized portable generators generally run $800 to $1,000. They’ll also run on average 10 to 12 hours on a 7 gallon tank of gas.


Large Portable Generators (8,500 to 15,000 watts with a couple of models coming in over 25,000 watts)

You can power everything that the other sizes can plus you can add a central air conditioner, a water heater, a range oven, or any other major item that is hardwired to your home if you have a transfer switch set up. You can also substitute something out and get your clothes dryer running. Units of this size usually run $1,000 – $2,500.


Stationary Permanently Installed Generators (10,000 to 45,000 watts)

These systems are fueled by propane, natural gas, or diesel and operate with very little interaction on your part. You can even connect them to your existing natural gas line so you don’t have to fill up any fuel tanks. They’ll usually turn on automatically in about 15 to 20 seconds after the power goes out. Stationary units will generally power most of the major items you use frequently in your home including the washer and dryer. Many will power your entire home.

These will cost you $3,000 to $15,000 or more, plus you’ll have to pay for installation by a certified electrician which will probably run you about $2,000. I don’t focus on stationary generators very much on this site but if you want to learn more I suggest you contact an electrician in your area. Make sure you get them to come out and personally inspect your house and your electric system to get an exact quote as power needs can vary greatly from house to house.


Important Features to Look For

Most portable generators on the market today have circuit breakers, fuel efficient engines, and automatic regulation of the voltage. Engines are typically four-cycle overhead valve types that are much more environmentally friendly than the old two-cycle engines that required you to mix oil with the gas. Overhead valve engines are also easier to start, produce less harmful emissions, last longer, and run quieter. Most of the controls and outlets will have weather protection as well.


Selecting An Alternator Type

When most people start looking for a portable generator, they think that the most important part of the machine is the engine. In reality it’s the alternator. The engine generates power and the alternator converts that power into electricity. There are two types of alternators: inverter and conventional.

Conventional alternators produce raw electricity that is not as clean as power coming from your utility company. They must maintain a constant speed (3,600 rpm) to produce AC power, and run at this maximum speed no matter what the power requirements are at the time. As a result they are much louder and use a lot more fuel than the inverter style. You don’t want to run sensitive electronics like computers and TV’s using conventional alternators as they can be damaged. The one positive is that conventional generators are cheaper to buy.

Inverter style alternators produce very clean AC power. They can run at varying speeds depending on the electrical needs at the time. As a result they are more fuel efficient, smaller, and quieter and can be used on sensitive electronics. They tend to be more expensive than conventional alternators though.

As far as the design of the alternator goes, experts suggest looking for an all metal, ball bearing alternator that incorporates a brushless design. Alternators that use ball bearings instead of needle bearings last much longer. Brushless alternators also last longer, require less maintenance and generate more efficient, cleaner energy, which is better for sensitive electrical devices like computers. All metal alternators, as opposed to plastic, will also have a longer life and are not as prone to warping and breakage.


Fuel Type

Portable generators will generally run on gasoline, propane, diesel, or natural gas. There are also some battery powered and solar powered systems on the market although these are not as common. Here are the pros and cons of each fuel type.

Gasoline

Pros

  • You can find gas anywhere, just go to your local station and fill up a container.
  • You can transport it easily with your generator.

Cons

  • Has a short shelf life.
  • Fueling stations may shut down during a blackout leaving you without gas if you don’t have some stored.
  • You need to preserve it using a stabilizer and store it far away from your house in a ventilated shed.


Propane

Pros

  • Burns clean
  • Last long and can be easily stored
  • You can get it delivered to your home if you have a large tank

Cons

  • You may have to use a converter kit if your generator is built for gasoline. These can cost on average a couple hundred dollars.
  • Produces less wattage than gas.


Natural Gas

Pros

  • If you have natural gas lines already to your home then you can just use that source
  • Burns clean

Cons

  • You may have to use a converter kit here as well.
  • Produces less wattage than propane and gasoline.


Diesel

Pros

  • You can also have this delivered to your home.
  • Diesel is the least flammable of all of the fossil fuel sources

Cons

  • Produces less wattage than gas.


Battery Inverter System

Pros

  • Quiet
  • You can put these units inside because they don’t generate any engine exhaust or carbon monoxide. The area should be well ventilated though because batteries can emit fumes.
  • Easy to start and run
  • Can last a long time because they don’t have any moving parts that can break down.

Cons

  • They don’t produce a lot of power so you can really only use battery powered generators for brief power outages or just to power a few small items.
  • Can cause problems with appliances that have built in clocks.


Changing and Adding Oil

It’s hard to keep track of when to do oil changes for your generator unless you write it down or your unit has an hour meter which keeps a record of how much total time the engine has run. It’s a bit easier to remember to add oil, but sometimes you may forget, especially if you haven’t run your generator in a while. So it’s good to have an automatic low-oil shutoff feature which will turn the generator off when the oil level drops below a set minimum so that the motor won’t be damaged.

You should also look for a spin-on oil filter which can help to reduce maintenance and help the engine last up to three times longer according to engine experts. Most modern portable generators will offer this feature, although it may cost more.


Sound Level

The noise level of your portable generator is an important factor to look at. You’re going to using it outside so you want to keep the peace with your neighbors as best you can and that means low noise levels. If you plan on using the portable generator in a national park, there are specific requirements on keeping sound levels below 60 decibels at a distance of 50 feet.

Look for generators that have a quiet mode and check the sound levels in normal mode as well. Most machines will have sound readings in the 45 to 80 decibel range with an average around 75. To give you an idea of what this means, 90 decibels is very loud, like a truck without a muffler. 80 decibels is loud, about like cars running at high speed (not as loud as a NASCAR race though). 70 decibels is about like normal street noise or your radio at an average noise level. 60 decibels is considered moderate, like the level of a normal conversation. 50 decibels is moderate as well, about what you would hear in an office. 40 decibels is faint, about what you would hear in a residential neighborhood without any cars coming through.


Portability

Most portable generators weigh between 30 and 70 pounds although some may go as high as 100 lbs. At 70 lbs many people will have a hard time picking the unit up. So you need to look for comfortable grips where two people can move it; or wheels where one person can push it around no problem. Units with pneumatic tires are even easier to roll around.


Some Additional Features To Look For

  • Electric Push Button Starter – Sometimes pull start engines can be a pain to get started so it’s best to have a push button battery powered starter for your generator.

  • Spark arrester – This is very important if you plan on camping or traveling with your generator. It can help prevent fires. Look for an arrester that is approved by the US Forest Service or Department of Agriculture.

  • Multiple Outlets – If you’re not using a transfer switch, then you are going to want four or more AC outlets for powering most of your home appliances and one DC outlet so you can power certain small electronic devices. Multiple outlets spread the load on the generator and give you more options to plug things in. Look for ground fault circuit interrupter lock-on outlets on the generator as these are the safest and OSHA approved.

  • Fuel Gauge – This is a nice feature to have, especially when the power is out for a long period of time. You can quickly just look at the gauge and see if you need to refill the tank or not with whichever fuel type your generator requires.

  • Idle control – You can reduce noise, fuel usage, and engine wear by using a generator with idle control. The idle control matches the amount of power that is needed so when there is a minimal amount of power being drawn from the alternator the engine will automatically throttle down.

  • Large fuel tank – You want something to match your needs, but larger fuel tanks certainly make things a little bit easier for you. A full 5 gallon tank will typically keep a generator running about 7 to 10 hours.

  • CARB Compliant – CARB stands for California Air Resources Board and products that do not meet this standard cannot be sold in California. Most manufacturers that offer this feature will promote it as a means to lower emissions which make this type of generator a more environmentally friendly product. If you live California you have to have a CARB compliant generator, if you live in one of the other 49 states in the US or outside of the country then you don’t have to have it but it’s still a very good feature to look for.



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One Comment »

  • Joe Lahoud said:

    A FOUND IT TO VERY HELPFUL…THANK YOU

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