An electrical generator employs a gas engine to turn a dynamo that generates electrical power. An inverter is a series of coils that convert direct-current electricity, such as from a car battery or a solar panel, into alternating-current voltages suited to household appliances. For instance, a semi-truck might use an inverter to power a miniature refrigerator; a car might use an inverter to power a laptop computer. An inverter generator, meanwhile, employs both a fueled engine and electricity-converting inverter.

Automobile battery terminal
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A car battery under the hood of a car.

Fuel Source

A generator drives the primary dynamo by an engine that typically uses gasoline or propane fuel. The engine must run continually to provide power; this consumes fuel and well as produces noise and air pollution. An inverter does not produce much noise and produces no air pollution. The inverter converts stored power to a standard current, usually 110 volts. A generator does not require an intermediate energy storage unit; it can provide constant power directly to a home. An inverter is strictly for conversion of existing power. Newer to the market are inverter generators that use gas to power a dynamo and a proprietary inverter to convert this power to useful AC voltage.

Generators Require More Maintenance

An engine-powered generator will require routine maintenance, such as oil changes and occasional rebuilds, while an inverter will usually not. The inverter simply uses fixed coils and circuitry to change electricity from one form into another. A generator is a complex moving mechanical assembly that can break down due to vibration or heat. Inverter generators incorporate both technologies, so they're as complex as generators.

Power Output

The size-to-power-output ratio is typically much higher for an inverter. Generators tend to be larger and heavier; they must be operated only in area with proper ventilation, as exhaust fumes will kill you. Power output for a large inverter ranges from 3,000 watts to 5,000 watts, while a generator matching that peak output would be many times the size of a comparable inverter. Some larger generators can produce in excess of 20,000 watts.

Peak Power

Generators are usually more tolerant of peak power spikes, instances in which the electrical use exceeds the power output of the unit. An engine-powered generator will surge but will typically keep running if the surge is brief. An inverter has an automatic shutdown circuit that cuts off power if the output is exceeded to prevent damage to the unit. This requires the user to inspect the unit and possibly reset its breaker fuse. Overcome this contingency by purchasing an inverter with many times the output required. Inverters get expensive at higher power range.

Longevity Varies

Inverters, having no moving parts, will typically outlast generators used equally. The advantage to having a generator instead of a separate inverter is repair; when an inverter breaks down, it almost always requires replacement because there are no serviceable parts. Inverter generators incorporate both technologies; they usually come with limited warranties that guarantee replacement or repair. Inverter generators are more expensive than either generators or inverters.