How to Select the Right Generator

Generators are relatively simple machines. In fact, they work much like your local electric power plant, but just on a much smaller scale. Power plants burn fuel, like coal, to spin turbines that generate electrical power; while generators burn fuel like gasoline, propane, natural gas, or diesel to power engines that produce electricity with the help of an alternator.

Let AP Electric help you choose the right generator for your needs.

What type of generator do you need?

Picking the right generator for you is a straight-forward process. Your first step is simply to determine what you want your new AP Electric generator to power. Do you want a generator for portable power needs during camping or tailgating? Do you need a generator to power your RV? Do you want to power only some of the appliances and devices in your home? Do you want to provide emergency power for your entire home? Will you be using the generator to power farm equipment or tools and equipment on jobsites? There are generators specifically designed for each of these uses and more. Let’s look at the main types of generators in the market, and how they can meet your needs:

Portable Generators

  • Portable generators are the perfect solution if you need a unit that you can move easily.
  • These generators are a popular means to provide power to areas with no access to the electrical grid.
  • Campers and tailgaters regularly use small hand-held generators to meet their electrical needs when enjoying the great outdoors or gathering to cheer on their home team.
  • These handy generators are becoming increasingly popular with homeowners who want a reliable power supply to help them during intermittent power outages.
  • Larger portable generators, sometimes powering mobile light towers, are often transported by trailer or pickup trucks to places like construction sites and outdoor events to get the job done.
  • Larger units can be provided with field selectable output voltage, making these generators a value choice when their usage or duty is variable.

Choose Your Portable Generator

Standby Generators

  • While portable generators offer a great solution for weathering the storm during brief power outages, standby generators are designed to protect your home or business from the personal and financial losses that can arise from prolonged power outages.
  • These generators are permanently mounted at your home or business and are meant to be used as a reliable backup supply of electricity for your home or business whenever your regular power source is down.
  • They are generally fueled by natural gas or liquid propane, offering prolonged run times when plumbed to your home’s natural gas supply or large-scale propane tank. These units can be wired to manual transfer devices, which require the owner to “transfer” between the utility and generator power or they can utilize automatic transfer switches to automatically start/stop when a utility loss in sensed, routing electricity into your home or business when needed.
  • Standby generators come in a variety of power output ratings, allowing owners to protect some or all of the electrical circuits in their homes and businesses.

Choose Your Residential Standby Generator OR Choose Your Commercial Standby Generator

RV Generators

  • While portable generators offer enough to provide power for your camping trip and tailgate party, if you are planning on traveling in style aboard your recreational vehicle (RV), you’ll want to use an RV generator. These generators are specifically designed to power your RV appliances along with all the accessories you are used to enjoying in your recreational vehicle including the smaller air conditioning units fitted to modern mobile homes.
  • RV generators are permanently mounted on your motorhome, trailer, or fifth wheel, and they run on gasoline, liquid propane, or diesel fuel.

Choose Your RV Generator

Off Grid and Prime Power Generators

  • Some generators are specifically designed and warranted to be used to provide power in Off Grid applications. Off grid applications are those locations that are not connected to the power grid and must generate their own power source using wind, sunlight, water or generators. These units can be wired to recharge solar battery systems on days when the sunlight alone isn’t enough to keep a full charge.
  • Prime Power generators can be used to provide off grid power in the absence of a solar battery storage system or to provide long duration run times for other uses. These engines are specifically made to handle these longer run times under load and offer extended service intervals to match.

Choose Your Off Grid or Prime Power Generator

PTO Generators

  • Generators are essentially engines that produce electricity with the help of an alternator. Well, Power Take-Off (PTO) generators are designed to produce electrical power on farms and ranches, where most people already own powerful engines in their tractors.
  • Therefore, PTO generators are basically just fancy alternators that can use a tractor’s engine to produce electricity.
  • These generators are specifically paired to the RPM profile of the owner’s farm implements to provide remote power for all kinds of agricultural uses.

Choose Your PTO Generator

What criteria should I consider when purchasing my generator?

Once you have decided what type of generator you are looking for, your next step is to familiarize yourself with some fundamental criteria that will enable you to make a final decision about the specific generator that is just the right match for your needs.

Some of the things to consider when properly sizing your generator:


You certainly want to know what wattage your generator should offer to fulfill your needs. This means knowing what you want to power and how much wattage those items need to start (starting watts) and run (running watts). Keep in mind that the wattage required for starting a tool or appliance with a motor will be much higher than the watts required to run that device. Things like Air Conditioners, Deep freezers, Well or Water Pumps and other devices require starting watts on the order of 3 to 4 times their running wattage.


The power output of your generator is given by its wattage rating, usually expressed as KW (Watts x 1000). Your generator should be sized to adequately handle ALL the devices and circuits you need to run from generator power AND include some spare KW capacity. Spare capacity is important to factor into your sizing because a motor that runs at LESS than full capacity can benefit from extended life, longer maintenance and service intervals and better fuel economy.

The power output of generators should be considered using two ratings:

Maximum Power

  • Maximum power is the maximum output that a generator can produce.
  • Your generator will usually only be able to maintain this output level for up to 30 minutes.

Rated Power

  • Rated power is the power that a generator can produce for long periods of time – typically 80% of the maximum power.
  • To determine the best size (power rating) generator for your needs, just add up the wattage needed for each device you want to power simultaneously. Or use each device one-at-a-time with a smaller generator.
  • Most electronic appliances and devices have this listed on a label affixed to the unit.


Below is a list of some common electric devices people like to power with their new generators:

  • Air Conditioner 3000w per ton starting watts – 1000w per ton running watts
  • Garage Doors 1000 – 1500 watts
  • Hair Dryer (1600 watts) 1900w, 1800w
  • Coffee Maker 600w, 600w
  • Electric Heater 1300w, 1300w
  • Electric Clothes Dryer 1500 watts
  • Dishwashers 1500 watts
  • Laptop computer 225w, 225w
  • Refrigerator / Freezer units 1200-1800 watts
  • Well Pumps – 750 watts per horsepower
  • Sump Pumps – 1500 watts
  • Furnaces – 250 watts
  • Microwaves 1500 watts
  • Big-screen and projector televisions (200-1000 watts), CD/DVD players (100 watts), and radios (10 watts)
  • Electric Ranges and Ovens – 1500 – 3000 watts
  • Light bulbs (60-75 watts/each) and outdoor light strings (250 watts)


Below is a list of some common devices people bring when tailgating, and their corresponding typical power requirements. The numbers show the starting power needed in watts, followed by their corresponding running power requirements (be sure to check the actual power needed for your particular device as it will be slightly different from the examples shown):

  • Crock-pots (240 watts) and hot plates (1200 watts)
  • Food processors (500 watts), small refrigerators (550 watts), and microwaves (1000 watts)
  • Big-screen and projector televisions (200-1000 watts), CD/DVD players (100 watts), and radios (10 watts)
  • Electric griddles (1500 watts) or an 8-inch electric stove (2100 watts)
  • Light bulbs (60-75 watts/each) and outdoor light strings (250 watts)
  • Game consoles (150 watts)
  • Cell phone and tablet battery chargers (5-25 watts)


You can run extension cords from your generator into your home or business. Alternatively, you can take a safer route and have an electrician install a transfer switch in your property’s electrical panel and apply the power from your generator into your circuit breaker.

The Transfer Switch

Standby generators are installed outdoors. The electricity they generate is routed from the unit and into your home or business via a transfer switch. If you want your generator to run through your property’s electrical wiring, then a transfer switch is a must.

The transfer switch is a simple device that “switches” power between Utility Power and Generator Power. When your utility power goes out, your automatic transfer switch senses it and starts your generator, when utility power is restored, the transfer switch automatically stops the generator.

When you select your switch, you will want to choose the amps that match your home’s main breaker. There is also more than one type of switch installation from which to choose: manual and automatic.

  • Manual: A manual transfer switch must be switched, manually, between utility power and generator power when the owner identifies an issue with the utility power supply. Further, the owner must manually switch back to utility power when utility power is restored. Manual switches are typically less expensive than automatic switches, but will NOT protect your home or business if you are not physically present to manually operate these switches.
  • Automatic: An automatic transfer switch operates automatically, transferring power between utility power and generator power by sensing the presence of both power sources. If your utility power supply is lost for more than 5 seconds, the automatic transfer switch starts the generator and when it is up to speed, transfer power to the generator source automatically. Automatic switches are typically more expensive than manual switches, but will protect your home or business whether you are physically present or not.
  • Service Entrance Rating explained: Both Automatic and Manual transfer switches come in Service Entrance rated and Non-Service Entrance rated versions. The National Electric code requires that a disconnect switch, which controls all power coming into a home or business must be within 5’ of and DIRECTLY in line behind the utility meter. If your transfer switch will be mounted adjacent to your meter and that meter does not contain a service disconnect switch, a Service Entrance rated transfer switch is required. Some areas of the country require that electric meters contain integrated service disconnect switches. In these areas, a non-service entrance rated transfer switch nay be used.


Your fuel and tank will determine your generator’s power and how long it will run on that fuel. So, find out what size fuel tank and type of fuel you need for what you want to accomplish.


Generators usually run on fuels like natural gas, liquid propane, diesel, or gasoline. Each type of fuel has its advantages and disadvantages:

  • Natural gas is unlimited, which means no refueling. It also burns clean and is environmentally-friendly.
  • Liquid propane also burns clean. In addition, it is easily kept in small containers and can be stored safely for a long time.
  • Diesel is a less flammable fuel. It also has the benefits of being readily available and somewhat less expensive than other fuels.
  • Gasoline is the most readily-available fuel source. It’s cheap and easy to store and carry; though it does not last as long.

Portable Generator Fuel

Most portable generators run on gasoline and other fuels, and some are multi-fueled with controls that allow switching from one fuel to another.

Commercial Standby Generator Fuel

These units are large, heavy-duty, stationary systems that generally function with engines fueled by diesel, natural gas or propane.

Residential Standby Generator Fuel

Standby home generators are installed outdoors and usually run on natural gas or propane.

RV Generator Fuel

  • RV generators run on fuel and you want to choose the one most compatible with your needs. For RVs powered by diesel, for example, you may want to go ahead and choose a diesel-powered generator so that you can depend on only one type of fuel during your trips. Of course, diesel is also cleaner and more powerful than standard gasoline, not to mention safer.
  • Liquid propane is also a good choice if you are concerned with the environment. And it has the added benefit of lasting longer in storage. However, it often does not last as long as other types of fuel.
  • Standard gasoline is popular because it’s cheaper and readily available. However, gas is more unsafe and does not last as long as diesel. So, it’s important to decide how much monetary costs means to you in these cases.

Run Time

  • The maximum time a generator can run before needing to be refueled is what manufacturers call run time. It is determined by the load applied, the efficiency of the generator, and the size of its gas tank.
  • Manufactures may provide the run time for both 1/4 rated load and full rated load, however some provide only the run time for 1/4 rated load because it appears much more impressive.
  • Your run time may vary significantly from manufacturer published specs due to the load draw. Remember, inverter generators will automatically throttle up and down when in use dependent upon the load, so consider the published specs a rough guideline only.



Your portable generator unit needs to have plenty of outlets to accommodate all the objects you want to run.


Find out what accessories you need to run your generator—cords, transfer switches, extra electrical panels, fuel tanks, battery charges, battery warmers, oil warmers, concrete pads, monitoring software, extended warranties, etc. —and ask yourself if your usage profile requires them.


Make sure you follow all city and neighborhood codes for power, installation, noise, etc.


Generators of every type are common in towns all across the United States, but that doesn’t mean they can’t be a nuisance sometimes, particularly when it comes to noise. In fact, your neighborhood or city may have noise regulations that your unit will need to conform to. Find out how loud your generator will be in decibels and compare that to any local regulations your location may have.

Manufacturers that provide noise level data usually report it in decibels (dBA), as in “59 dBA”. Sometimes, noise data can also be reported as a range, as in “53 – 59 dBA”. When a range of numbers is given, it means the noise level at 1/4 rated load and the noise level at full rated load. Beware, some manufacturers advertise how quiet their generator performs using only the 1/4 rated load number. So, be sure to evaluate your generator at FULL rated load – that’s when it produces the loudest noise.

The table below shows how common noises compare to each other with respect to dBA levels. Keep in mind that the distance away from the sound source directly affects how loud it sounds. Most popular 1,000 – 2,000 watt inverter generators generate 50-60 dBA noise level at full rated load and are considered to be about as loud as normal conversational speech.

Decibel Rating


The best way to install and operate your new generator safely is to get professional help. However, you need to know general safety no matter what. So, remember these rules when operating your unit:

  • Never try to install your generator into your house’s wiring. Hire and electrician to connect your unit with an automatic transfer switch and install the generator. This protects you, your home’s wiring, and power company employees working on the lines.
  • Buy and use heavy-duty extension cords to avoid overloading and heat damage. Make sure to arrange them so that no one trips. Be extra careful with extension cords around moisture.
  • Plug your devices and appliances directly into the generator.
  • Don’t run your unit indoors. Your generator needs plenty of ventilation.
  • Add fuel while the generator is off, and never while it’s running. Be careful not to spill your fuel, and never keep cigarettes or other lit objects near your unit. Keep a fire extinguisher nearby. Also, tri-fuel generators help you avoid having to refuel as often.
  • Don’t overuse your generator. Use it only when you need it.