Power Generation Definitions

Common ground for talking points related to Portable and Standby Generators. Review this section to understand the specific terms for Power Generation definitions encountered.

Portable Generator Or Generation

Portable Refers to a machine of any size that can be moved to a location to provide power. It can have any number of configurations, and fuel is supplied to small tank (relative) on the generator or hooked to it. The generator can weight under 50 lbs. or into the hundreds of pounds. Trailered generators can be thousands of pounds, but are large and not necessarily covered in the intent of this guide.

Standby Generator (sometimes referred to as emergency backup generation)

A standby generator may be portable, but in most cases it is considered a fixed asset that is connected to a fixed fuel source. Standby generation refers to a unit that’s main purpose is to provide power if the utility power goes off. In many cases it has an automated system that operates when it senses line power is lost. Some setups have auto exercise features that test the unit on a period basis.  Manual start standby generation is also a possible configuration.

Genie – Short for generator, portable or standby.

AC Power 

Alternating Current Power produced via an alternator or coil generator. It means the flow of electric charge periodically reverse direction. This is the power supplied to your home.

DC Power

DC Power is Direct Current power; think of this as a battery in your car. DC is the flow of electric charge and is only in one direction. Converters/inverters can change AC to DC and visa-a-versa. Much of your electrical equipment is DC power and the chargers you use are transformers to convert high voltage AC power to low voltage DC. Batteries used in your small electric equipment use direct current.

Inverter Power Generation

Inverter power generation is the process of converting stable direct current (DC) power into AC power. This gives the power a low distortion (THD <5%) and is referred to as high quality or sine wave power. Often marketed for sensitive electronics.

Watts, Volts, Amps

Voltage (Volts, V) is the expression of, or representation of electric potential energy per unit charge.  It is measurement of energy within an electric field. For our purposes it is the level provided to your appliances or house.

Amperage (amps, A) is measurement for electric current, the higher the amps the more likely you are to be electrocuted.

Watts (W) also known as Power and is calculated by Volts times Amps (current).

Single Phase Power

In residential, small tool, or most circumstances for small to medium commercial applications the equipment is single phase. The power supplied to your house is single phase.

3 phase Power

This is the generation of 3 AC electric currents. They have a phased separation of 120 degrees apart. 3-phase current is used to drive larger motors for starting purposes and most automotive alternates use 3 phase power and rectify it to DC power.

If you have 3 phase power equipment or supply you are working with heavy loads or large motors and is usually more cost effective than an equivalent single phase of the same voltage.  You should seek a professional electrician or engineering help if you are using 3 phase systems. In the residential market you will not use 3 phase systems.

Total Harmonic Distortion (THD)

Total Harmonic Distortion is the stated measurement related to the quality of electricity. “Clean electricity” is considered for a THD of less than 6% and often stated at 5% or less. For units that measure greater than 6% THD the electricity can cause sensitive electrical circuits to lose life such as computers or other minor electronics, which may malfunction or operate improperly. It is common for standard generators to be in the 9% range and some to produce THD greater than 15%.

Fuel Source and Types

The place you get fuel that runs your generator.

Gasoline (gas) is the common fuel that runs automobile engines. Many portable generators run on this fuel due to its availability and common small engine configurations.

Diesel fuel as used by many large semi-trailer trucks and other automobiles. This is also a common fuel and there are several portable generators that use this fuel.

Liquid Propane generally refers to the exact same fuel that you use for your gas grill or small burner. It is stored in small 20 lb. cylinders to very large 300 to 1000 lb. and larger vessels.

Natural Gas is the same fuel that supplies many homes for cooking and heating. It is a common way to connect standby generators as the gas supply is not affected by power outages. Natural Gas supply has its own backup power system.

Solar power is the process of using solar panels to produce DC current directly from sunlight. Alternately there are solar heat conversion systems, but the panel is the common method of producing small amounts of power for small equipment.

Wind is used to turn wind turbines and there are a number of smaller models for use in the applications presented here. They do not produce large amounts of power unless you have a 100 foot tall pole with 30 foot blades and a 500kW to 3MW turbine.  Yup the big ones you see along the highway are utility grade. The unpredictability of the wind makes this an alternate power that requires a backup of its own.


Battery backup power comes in various sizes and is intended for short term use to power small equipment and some appliances such as garage door openers. It can be purchased in various sizes and configured as an uninterruptable power source (UPS) to keep computer or other sensitive equipment running for long enough to restore power or safely shutdown them down. In your laptop your battery can act like a UPS.

Power Extension Cord or Power Cord

We are all familiar with extension cords we use them all the time in our house to connect computer equipment and stereos to a single outlet. In Portable generation a power cord can have a very distinct meaning when it comes to connecting to your generator. A 5-20 cord vs. a L5-30, vs. a L14-30 all have limitations and connectivity methods. This becomes important when you decide on your output configuration of the generator.

Wire Gauge

There are an extensive number of sites covering wire gauge. It simple means how large a wire is in diameter or cross-section (area). Typically when we talk of wire gauge we use the American Wire Gauge (AWG) which refers to the diameters of electrically conducting wire. The formula is a bit elaborate, but it practice, the larger the gauge number the smaller the wire. As an example a #8 gauge wire has a diameter of about 1/8 inch. A #2 gauge wire has a diameter of ¼ inch.

Transfer Switch or Panel

A transfer switch or panel refers to an electrical box that allows you to connect a generator 120/240V electric connection to your house via an interconnection to your main utility panel. (These boxes are normally wired via a certified electrician and regulated by code in many jurisdictions; consult with your local officials prior to installing)

It allows you to connect either portable or standby generators directly to your home or through a plug to provide power to various circuits in your house, As well you can manage which circuits may have power available from the source.

Bus Bar

Literally this is a bar or pipe that allow an electrical connection input and distributes it to multiple circuits.  For our purposes it describes the internal conductor that distributes electricity to switches/breakers.

Inlet box

An inlet box provides a means to connect your generator with a power cord to an outside plug that then connects to a transfer switch.


These power generation definitions and terms represent the most basic that are needed to begin your journey into the generation arena. Let me know if you need more terms defined. Contact us


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