How Does an Inverter Generator Work?

If you’re shopping for a portable off-grid generator or home backup power solution, you’ve probably heard of inverters.

Inverters are an essential component in solar power systems and are also used to improve numerous aspects of engine generators that burn petrol or other fossil fuels.

Like traditional fossil fuel generators, an inverter generator burns fossil fuels like propane and petrol with an engine and uses an alternator to produce electricity. 

Unlike older engine generators, Inverters convert the alternating current (AC) produced by the mechanical generator into direct current (DC) and back to AC again for output.

The conversion process provides numerous benefits, which we’ll explore below. 

How Do Inverter Generators Work?

Inverter generators use the same basic principle as traditional fossil fuel generators — and, at a larger scale, the steam, gas, and wind turbines that provide most of the world’s electricity today.

(Source: Royal Institution Great Britain. Photo by Paul Wilkinson)

The first electric generator was invented in 1831 by Michael Faraday.

Faraday discovered the principle of electromagnetic induction — the relationship between magnetism and motion known as Faraday’s Law — which all turbines and generators (except solar and fuel cell) use to produce electricity.

According to the Royal Institute of Great Britain: 

“Virtually all electric power is produced using Faraday’s principles, no matter whether the prime source of energy is coal, oil, gas, nuclear, hydro, or wind: all these fuels are used to drive a generator (or turbine) which generates the electrical current.”

Solar panel systems are different and convert sunlight into electricity using the photovoltaic effect. 

Portable engine generators that burn fossil fuels — including inverter generators — produce electricity the same way and share many similar components.

Let’s take a closer look.

The Core Components

All standalone petrol, propane, and diesel generators require fuel, an engine, and an electromagnetic alternator to produce electricity.

Inverter generators need all three, plus additional components that process and condition alternating current (AC) electricity to achieve the desired benefits. 

Here’s what’s under the hood.

Fuel Source (Petrol Tank)

Portable generators store fuel — such as petrol, propane, or diesel — in a tank for consumption.

Standby generators may use natural gas lines from a utility company instead of relying on a tank for storage.

Regardless, conventional petrol, LPG, diesel, and inverter generators won’t run without fuel. 

Starter

A starter is required to provide a short burst of electricity — a spark — to ignite the fuel for a petrol generator’s internal combustion engine. 

Once the combustion — or burning — process has started, the generator should run until it runs out of fuel.   

Traditional generators relied on a manual starting process, such as a pull cord or recoil rope.

You can still purchase manual start generators today, but most inverter generators have digital or automatic starters.

Internal Combustion Engine

An engine is essential to all conventional and inverter generators that burn fossil fuel.

The internal combustion engines found in electric generators are similar to engines in gas-powered automobiles.  

The starter and engine convert the chemical energy from burning fuel into mechanical (potential + kinetic) energy.

A rotating engine shaft (prime mover) produces mechanical energy and passes it through an electromagnetic field (alternator), inducing alternating current (AC) electricity. 

The speed at which the prime mover rotates determines the current’s output frequency.  

Alternator

The alternator in an engine generator is sometimes referred to simply as the generator and the combination as a gen-set.

An alternator comprises two parts, one stationary (stator) and one that rotates (rotor).

The rotating magnetic field produced by the rotor induces an AC voltage in the stator’s stationery wire, as proven by Faraday’s Law. 

Voltage Regulator (AVR)

The raw AC electricity produced by an engine and alternator fluctuates widely — it’s too inconsistent to power devices and appliances safely. 

In modern portable generators, an automatic voltage regulator (AVR) ensures the AC output is suitable for use. 

Inverter*

Even with an AVR, conventional fossil fuel generators produce “dirty power.”

In this context, “dirty” doesn’t refer to the toxic and greenhouse gas emissions produced by burning fossil fuels.

Instead, it refers to electrical fluctuations and surges that damage sensitive electronics.

The “noise” in AC output is measured as total harmonic distortion (THD).

Traditional fossil fuel generators produce AC output with up to 25% THD — far too “dirty” for digital devices — let alone computers and hard drives.

That’s where an inverter comes in.

Inverter generators use a rectifier to convert raw AC power into direct current and back to AC for output, significantly reducing THD.

Conventional inverter generators can reduce THD to 1%, resulting in much cleaner power and additional benefits outlined below.

* Only used in inverter generators

Power or Control Panel

Traditional petrol and LPG generators skip the additional processing and power conditioning an inverter provides.  

After passing through the automatic voltage regulator — and potentially other power conditioning components — alternating current is output for use.

Depending on your chosen model, you can plug appliances directly into the generator or integrate the generator with your home circuitry using a transfer switch for backup power during blackouts.

Most modern generators — with or without an inverter — offer a power panel that allows you to control certain operations, such as a timer and automatic shutdown.

What are the Main Differences Between an Inverter Generator and Traditional Generators?

Traditional and inverter generators have far more in common than many people think.

Both rely on an engine that burns fossil fuels like petrol, diesel, and propane to convert chemical power into mechanical power and an alternator to produce alternating current (AC) electricity.

Inverter generators have additional components and add at least one step to the AC output process.

By converting AC to direct current (DC) electricity and back to AC for output, inverters differ from conventional generators in the following ways.

Fuel Efficiency

Traditional fossil fuel generators only run at full speed.

A 2000W petrol generator consumes enough fuel to produce 2000W AC output whenever it’s running — regardless of how much electricity you consume.

For example, if you only use 1000W of AC output at any given time, half of the electricity the 2000W generator produces goes to waste.

Inverter generators, on the other hand, throttle up and down based on your electricity consumption.

An inverter generator can significantly reduce fuel consumption and costs if you frequently use a generator at less than its maximum output capacity.  

For many people, fuel efficiency is the#1 reason they opt for an inverter generator over conventional portable generators.

“Cleaner” Power

The electricity produced by traditional generators is often referred to as “dirty” power.

Not because of greenhouse gas emissions or toxic fumes…

Thanks to better efficiency, inverter generators may produce slightly less of each, but they still burn fossil fuels like petrol or propane.

In this context, the “cleaner” energy that inverters provide isn’t about fuel. 

It’s about AC output quality.

By skipping the inversion process, traditional generators send largely unprocessed AC power to the outputs or transfer switch.

This results in electricity that varies in voltage and current and that’s prone to surges.

The “dirtiness” of electric current is measured by total harmonic distortion, which can reach 25% or higher in conventional generators. 

Harmonic distortion — particularly power surges — makes many conventional generators ill-suited or even dangerous for use with sensitive electronics.

Computer servers and hard drives are often cited as particularly prone to damage from dirty power.

However, many household appliances, medical devices, and personal electronics are susceptible to harm from fluctuations and surges in power.

Inverter generators minimise THD and produce cleaner electricity by converting raw alternating current produced by the engine and alternator to DC electricity and back to AC for output. 

Reduced Toxic and Greenhouse Gas Emissions

Unlike solar generators, inverters still rely on burning fossil fuels to produce electricity.

However, because inverter generators throttle up or down based on consumption, they produce less toxic and greenhouse gas emissions than conventional generators under light and medium load conditions.

Additionally, many inverter generators use propane (LPG) as fuel.

LPG burns significantly cleaner than petrol or diesel and is less harmful to the environment.

It’s essential to note, however…

No generator that burns fossil fuels can be operated indoors.

Improper use of petrol generators — including inverters — poisons thousands of people each year with carbon monoxide, many of whom die.

Parallel Compatibility

Generally, inverters offer lower power output than traditional petrol or diesel generators. 

Most inverter generators sold provide from 1500W to 3500 watts of AC output.

This has traditionally meant that inverters are used for portable applications while traditional generators are used for high-wattage applications like standby and whole-home backup power.

One way to circumvent inverters’ output limitations is to chain multiple units of the same size and type together in parallel.  

For example, if you chain two 2200W inverter generators together following the manufacturer’s instructions, you can double your rated power output to 4400W.

Hybrid inverter generators that offer battery storage and multiple charging options — including petrol, propane, solar, and AC power — are an even better option for portable and high-wattage applications.  

Portability

Inverter generators tend to be more lightweight and compact than conventional petrol generators. 

Increased portability makes them a solid choice for relatively low-wattage off-grid and motorhome applications where ease of transport is a factor.

(Source: Hearing Health Foundation)

Quieter Operation

Inverter generators are significantly quieter than traditional petrol and diesel generators, partly because they don’t always run at full throttle.

Closed-frame inverter generators can operate at under 60 decibels.

However, they remain significantly louder than portable power stations, like EcoFlow’s DELTA 2 Max, which operates at only 30dB, equal to average room noise.

The Pros and Cons of Inverter Generators

Inverters have numerous advantages over conventional petrol generators — especially under light electrical loads and in portable applications.

But they do come with some drawbacks.

Read on to find out more about the pros and cons of inverter generators.

Pros

1. Lower Fuel Consumption: The primary advantage of inverters over traditional fossil fuel generators is their ability to throttle up and down based on electricity consumption. If you frequently run devices and appliances that operate less than your generator’s maximum output capacity, you’ll see improved fuel efficiency and spend less on propane or petrol.  
2. Less “Dirty” Power: If you’re using a generator for power tools and other mechanical devices, how “clean” the AC output is may not make much difference. However, power surges and high total harmonic distortion (THD) can damage your valuable equipment if you charge or operate sensitive electronics and digital devices. By converting AC to DC and back to AC again, inverters can produce output with minimal THD. Some inverter generators can achieve pure sine wave output — the gold standard of AC electricity.

3. Quieter Operation: Conventional generators are extremely loud. Inverters can operate up to 20dB lower than traditional petrol and diesel generators. If you use a petrol generator at campsites or other communal areas, noise will likely prevent you from running it at night. Inverter generators and portable power stations are better suited to low-noise applications. 

Cons

1. High Cost: Inverters require additional components that traditional portable generators don’t and tend to have a higher sticker price. However, reduced fuel costs under light loads can save you money in the long run.
2. Unsafe for Indoor Use: No generator that burns fossil fuels — including inverters — can be used indoors. If you need off-grid electricity that you can use indoors, a portable power station or solar generator is the best choice. 
3. Limited AC Output Wattage: Inverters have limited AC output wattage compared to conventional generators.  You can get around this limitation by chaining inverters in parallel, but that will increase your costs.

How to Choose the Right Inverter Generator

There is no “one-size-fits-all” answer to the question of which inverter generator is best for you.

It really does depend on your use case.

Here are the essential factors to consider before making a purchase decision.

• AC Output: Calculate the total starting and running wattage of all the appliances you want to operate simultaneously in watts or kilowatts. Make sure the AC output of the generator exceeds that total by at least 10% 
• Electricity Consumption: Once you’ve determined which devices and appliances you want to run, you need to estimate their running time. Electricity consumption over time is measured in watt-hours (wH) and kilowatt hours (kWh).  Learn how to calculate electricity consumption here. 
• Storage Capacity: How long do you need your inverter generator to run between refills of propane or petrol? Remember, propane is much easier and safer to store than petrol. The manufacturer should provide you with an estimate of how many kWh of electricity a single tank will provide before running out.

Hybrid Inverter Generator + Battery Storage

If you’re considering an inverter over a conventional petrol or LPG generator, it’s a safe bet that fuel efficiency and clean power output are a concern.

Did you know that there’s an even better choice?

EcoFlow’s DELTA Pro 3 allows you to fast-charge using an inverter or a conventional petrol or LPG generator, plus five additional charging methods — including an 800W alternator charger, solar panels and household AC power.

A hybrid inverter + portable power station solution backs up your essential high-wattage appliances for home energy security during a blackout or provides portable power on the road. 

If you want a generator primarily for home backup power, you must consider that access to fuel may be restricted during emergency situations or unavailable altogether.

Opting for a hybrid inverter + storage system gives you all the benefits of traditional inverter generators, plus much more.

Frequently Asked Questions

Final Thoughts

When conventional inverter generators first appeared on the market, they represented a significant upgrade on traditional petrol and LPG generators for many applications.

Today, EcoFlow’s DELTA Pro 3 is a much better solution that allows you to recharge with a fossil fuel generator and offers many more benefits at a similar cost.

Whether you’re looking for a portable off-grid generator or whole-home backup power, EcoFlow has a solution for you.

Check out our selection today.