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The Ins and Outs of Generators: The Types of Generators and Proper Maintenance

Grainger Editorial Staff

Blackouts. Brownouts. Permanent faults. All of these power outages wreak havoc onto homes and businesses. They can cut into precious hours of work and inhibit the appliances that keep people safe during periods of intense heat and frigidity. Worst of all is when power outages occur during electrically powered medical procedures. That's where electric generators come in.

What does a generator do?

Electric generators are, essentially, life savers. They are backup power sources that convert fuel supply—usually propane, diesel or gasoline, into electrical energy. They are the primary sources of electrical supply during power outages. This energy is used in an external circuit. Unlike standby generators, the following are not permanently installed in one place, so they’re easy to start.

Types of Generators

There are three main types of generators: portable, inverter and standby. Despite their differences, all these generators should undergo similar generator maintenance to ensure long-term usability, and similar safety precautions should be taken to reduce the hazards posed by their operation.

Portable Generator

A portable generator is powered by gas or diesel fuel and can provide temporary electrical power.

Here are some characteristics to note about these types of generators:

  • Uses a combustion engine to conduct electricity.
  • Can plug into electrical appliances or tools via its sockets.
  • Can be wired into a facility’s subpanels.
  • Can be used in remote sites.
  • Has enough power to run a television, freezer and refrigerator.
  • The engine should run at 3600 rpm to render the standard 60hz of current.
  • Use a governor to control the engine’s speed.
  • Can power tools and lights.

Inverter Generator

An inverter generator uses an engine connected to an alternator to produce AC power. It also uses a rectifier unlike other generators to convert the AC power into DC power.

Here are some characteristics to note about these types of generators:

  • Relies on high-tech magnets.
  • Uses advanced electronic circuitry.
  • Undergoes three phases to produce electricity.
  • Outputs AC current, convert it to DC current and finally invert it to AC.
  • Maintains a constant flowing of current to an appliance.
  • Is more energy-efficient, as the engine speed adjusts itself according to how much power is needed.
  • Its AC can be set to any voltage and frequency when used with proper equipment.
  • Tends to be little and lightweight.
  • Can fit into a car, RV or boat.

Standby Generator

A standby generator is an electrical system that operates with an automatic transfer switch that commands it to power a device up during power loss.

Here are some characteristics to note about these types of generators:

  • Operates automatically.
  • Delivers permanent power protection.
  • Has two components: a standby generator and an automatic transfer switch.
  • Can operate on liquid propane or natural gas.
  • Will run on the fuel type already in use in the facility or home.
  • Uses an internal combustion engine.
  • Senses the power loss within seconds and boots up electricity so that power loss is felt very briefly.
  • Executes automatic weekly self-tests to see that it is properly reacting to a power loss.
  • Is constantly monitoring utility power.
  • Used in safety systems for elevators, standby lighting, medical and life support equipment and fire protection systems.

Best Generator for Different Outages

Generator Type

Best Use

Portable Generator Refrigerators, spray gun systems, nail guns
Inverter Generator Car batteries, laptops
Standby Generator Emergency settings, hospital machinery

Generator Maintenance

Maintaining a generator is a relatively similar process among the three major types of engines. First, it is vital to follow the maintenance schedule of the manufacturer with each type of generator. A routine maintenance practice is that of general inspection. Inspections consist of checking for leaks, assessing oil and coolant levels, glancing at the belts and hoses and checking the battery terminals and cables. It is important to inspect the oil as well, as it must be changed regularly. Oil change frequency depends on the manufacturer, how often the generator is used and your work environment. Typically, it is recommended you change the oil after 100 hours of operation, especially if the generator uses diesel.

Generator maintenance requires:

  • Annual fuel cleaning and filtering, as diesel fuel degrades quickly. After a few weeks of operation, diesel fuel degrades via contamination of water and microbes, resulting in clogged fuel lines and filters. Fuel cleaning involves using biocides annually in all generators except for the standby generator, in which it will attract moisture.
  • The cooling system to be maintained, which requires checking the coolant level at existing intervals. This must be done during shutdown periods.
  • Checking for battery power; this is especially true for standby generators, as battery issues are their primary cause of failure. Make sure the batteries are robust and charged enough to last long so as to not incur any start-up hitches for the generator.
  • Regular testing to inform of the battery’s current status. Testing involves checking the electrolyte levels and specific gravity of the batteries. The batteries themselves also must be clean.

Further Care and Maintenance of Generators

Besides the above best practices, it is also important to exorcise the generator on a weekly basis for 30 minutes under load. This will charge the battery, remove excess wetness, lubricate the engine and filter the fuel and foil. Any loose pieces found anywhere on the generator must be placed securely in.

You should also keep records of inspections and tests for future inspections and scrutiny. These records will allow you to stay in the know of your generator’s state.


The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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