AC vs DC Generators: Your Guide To Choosing the Best Generator

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Generators come in different designs, fuel types, and applications, but we can only classify these machines into two, AC and DC, in terms of power generation.

So, which one is right for you: AC vs DC generators?

Does it matter to know the difference? How does an AC generator work? How about a DC model? These are just some of the things you want to know.

AC vs DC might be one of those topics you used to hate in your physics class in high school. Your knowledge about alternating current (AC) and direct current (DC) can help you find the right generator for your application needs.

Let’s talk about AC and DC, particularly their key differences, advantages, and drawbacks. We’ll also show you the most common applications of both AC and DC generators.

Which Is Better AC or DC Generator?

Which performs better between AC generator vs DC generator? 

AC vs DC Generators

In your quest for the best generators, you must have encountered AC and DC units so many times. To understand their difference, you should first learn how each generates power.

This isn’t going to be a dragging discussion like those you used to have in high school. Let us try to explain things in a simpler and relevant way.

How Generator Works

A generator works by converting mechanical energy into electrical energy. Note that this amazing device does not actually “create” electricity.

Instead, it utilizes the mechanical energy from an external source to induce the movement of electric charges present in the wires. The electric charges then run through an external electric circuit, producing power as output.

Generators adopt the concept of “electromagnetic induction” discovered by Michael Faraday from 1831 to 1832 [1]. Thanks to him, today, we can supply power to our homes and businesses even during emergencies or natural calamities.

While the process of electromagnetic induction sounds plain and simple, many components have to work in sync for it to happen. These include the generator’s engine, fuel system, alternator, and so on.

We’ll not discuss each one in detail. We need you to focus on the alternator.

Also known as the gearhead, the alternator is the part of the generator that produces the electrical output. The alternator has several tiny things that work together to cause the relative movement between the magnetic and electrical fields. 

Based on the output, electric generators produce either alternating current or direct current. As their names suggest, AC vs DC generator’s main difference is the direction of the electric current.

Let’s dig deeper into how each type of generator works, its advantages, and its drawbacks.

How Does an AC Generator Work?

Ac Generator

Overall, the most common backup generators are AC generators. An AC generator is consists of a coil of wire that rotates or moves around a fixed magnet. 

Here’s how the electrical current moves in an AC generator:

  1. The coil rotates in the magnetic field.
  2. Electrical charges present in the wire get induced to move around the roto coil or windings.
  3. The hollow rings connected to the end of the coil helps rotate and provide electric contact with the brushes.
  4. The current is carried outside the generator through the brushes which are connected to the slip rings.
  5. Current flows in the external circuit.

As the coil of wire rotates, one side will have an upward motion, and another will have a downward movement. Hence, the current flows in opposite directions, flowing around the loop. At every half turn, the current flows through a loop, producing alternating current.

What Are the Advantages of AC Generators?

For a large part, AC generators have very simple structures, so they are easier to maintain. They also operate quietly, and less energy gets lost during the conversion process.

AC generators also tend to have a longer lifespan than DC generators with a commutator and carbon brushes. You can even convert AC to other voltages with the use of transformers. Lastly, they require less maintenance.

What Are the Drawbacks of AC Generators?

Generators that utilize AC motors need additional insulation because of the massive amount of voltage needed to supply a fixed level of power. They are also more prone to overheating and sparks due to higher currents produced.

How Does a DC Generator Work?

DC Generator

A simple DC generator features a coil of wire that rotates in a magnetic field. However, instead of slip rings found in an AC generator, it uses a split ring or commutator.

The split ring reverses the direction of the current that flows through the coil every half rotation. This forces the current to flow in the same direction.

In a DC motor, the input power is not completely transformed into output power. Most of it gets lost along the way.

What Are the Advantages of DC Generators?

These generators have a simple design and can run large motors. The electricity they produce is consistent. DC generators also have a high terminal load, and they produce fewer fluctuations by smoothing the output voltage.

What Are the Drawbacks of DC Generators?

You can apply DC generators to a transformer. Also, the whole power input cannot be converted into power output because some power gets lost during the conversion process. Lastly, a voltage drop is common over long distances.

Are AC or DC Generators More Efficient?

DC generators are less efficient than AC units because of sparking and energy losses. Different forms of energy loss take place during the conversion. These include:

  • Copper Losses: These occur in the armature and field copper windings due to brush contact resistance.
  • Mechanical Losses: The losses caused by friction in bearings and commutator account for 10% to 20% of full load losses.
  • Core Losses: These occur in the armature iron core as it rotates in the magnetic field and induces the core to itself too.

Why Are Small Generators AC Rather Than DC?

DC generators provide a reliable energy supply that’s capable of producing a large output range ideal for powering large motors. Even batteries used for off-grids can be charged using DC generators.

Meanwhile, AC generators produce an output voltage that differs in time and amplitude (distance of electric waves). Depending on the power output requirement, an AC generator can supply only the power output needed to run appliances and devices at specific times. 

Therefore, they are more suitable for powering smaller equipment and appliances.

AC Generator vs DC Generator: How Are AC and DC Generators Different?

To determine how different these two generators are, let’s look at their main points of difference.

Direction of Current

A generator is classified as AC or DC according to the direction of the electrical current generated. 

An AC generator produces electrical energy in the form of an alternating current. In other words, the direction of the electrical current reverses periodically. 

Alternating current is what electric companies supply to homes and businesses. Meanwhile, a DC generator produces an electrical current in one direction only.

Alternator Design

Both AC and DC generators work on the principle of electromagnetic induction. However, each has an alternator designed differently.

In an AC generator, the electrical current flows through a fixed coil and a moving magnetic field. In a DC unit, the current flows through a rotating coil in a permanent magnetic field.

Both AC and DC generators feature a simple design, but the latter is far more costly and complex to construct due to the components needed to make the current flow in one direction, such as the commutators and slip rings involved.

Output Voltage and Power Output

Another important thing to know about DC generators vs AC generator is their output voltage. AC generators produce a high voltage, ranging from 50Hz to 60Hz, and vary in amplitude and time. 

On the other hand, DC generators produce a low voltage, regardless of amplitude and time.

The output from an AC generator can be easily transmitted using a transformer. Meanwhile, a DC generator uses a special distribution system, either a two-wire DC or a three-wire DC system.


AC generators are primarily used for supplying power to smaller electrical items in your home or business, such as your home appliances, computers, or power tools. 

Most portable generators use an engine that transforms fuel, gas, diesel, propane, or natural gas, into alternating electrical current.

A DC generator is used as a backup power source for larger electric motors, such as industrial welding machines, DC locomotives, and other power equipment like those used in subway systems. 

It’s the generator type used in large-scale commercial job sites.

The Case of Inverter Generators

ryobi inverter generator

Now that you know how are AC and DC generators different, let us introduce you to a more recent model of generators: the inverter types.

These generators are touted for being more quiet, compact, lightweight, safe, and, most importantly, more fuel-efficient. They are also more eco-friendly.

Unlike traditional generators that produce either alternating current or direct current, inverter generators work differently.

In this type of generator, DC is converted into AC power through the use of a rectifier. The DC power is inverted back to AC by a computer inside the generator before it is sent to the control panel.

Since a computer controls the power, inverter generators have lower total harmonic distortion (THD), creating “cleaner” sine waves needed to safely power sensitive devices like televisions, computers, and smartphones.

Related: How to make portable generator power clean.

Can You Convert an AC Generator To DC?

Converting is difficult, but it can be done. There are two methods to convert an AC generator into a DC generator.

One is by using a rectifier like that in the inverter type. Another is by replacing certain components of the AC generator. For example, you can replace the slip rings with split rings.

AC vs DC Generators: Wrapping It Up

Generators come in two categories: standby and portable. (Click here to read which one is the best for home use)

Each type has different subcategories and wattage ratings. There are also “commercial” generators used in large-scale onsite projects.

While backup power generators differ in designs and functions, they are typically differentiated as either AC or DC. AC and DC generators serve two completely different purposes. Depending on your application needs, you might need an AC or a DC generator.

AC generators are mainly used to power smaller appliances, such as those we use at home. DC generators are used to power large motors so they are more often used in commercial and industrial settings.

Both AC and DC generators transform mechanical energy into electrical energy. They follow the same concept of EMF (Electromotive force) induced by a rotating or moving coil through a magnetic field.

So, DC generator vs AC generator, what’s the real deal? 

Overall, AC generators are the most common backup generators, but if you’re looking for a power backup solution for your business, you might consider a DC generator. Your decision will ultimately come down to your power needs.