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PWM Fans vs DC Fans: What’s the Difference?

PWM Fan vs DC FanAre you in the market for some new case fans? Unsure of whether you should get PWM fans or DC fans? In this post, we highlight the differences between DC fans and PWM fans to help you determine which option is best for you.

Fans are an important part of any computer system. The reason is simple: the successful operation of a computer is a game of heat management.

While there are some components that operate more efficiently at a certain level of heat, as a rule of thumb, the cooler you’re able to keep your system, the greater its performance—it’s why those Nitrogen-Cooled CPU videos exist.

While far less extreme, fans operate under this directive. Whether they’re pulling in cool air from the exterior of the case, or expelling it from the interior, they play a vital part in keeping a computer within safe operating temperature.

Despite looking nearly identical, there’s two main variants of fans used in computers: PWM (Pulse Width Modulation) fans, which have 4 pins, and DC (Direct Current) fans, which have 3 pins.

Considering how important it is for computers to run within their “safe zone”, so to speak, it begs the question: Which option is better? PWM fans or DC fans?

PWM Fans vs DC Fans

Technically speaking, PWM fans are strictly superior to DC fans in nearly every metric—performance, durability, and power efficiency—so it might surprise you to hear that if fans were included with your case, they’re most likely DC fans, with the exception of the CPU fan.

There’s a few reasons why this is the case.

Generally speaking, the faster a fan is spinning (measured in RPM), the cooler a system is. Neither PWM nor DC fans are an exception to this.

So why are PWM fans strictly better—at least, in most cases? There’s a few reasons.

PWM Fans Are Typically Better

The biggest of these reasons is the aforementioned 4th pin present in PWM fans. This 4th pin allows PWM fans to run what is called a duty cycle—which ties into another major difference—the voltage.

As stated previously, the faster a fan spins, the cooler the system. And while there’s little to no difference between the RPMs of different fan types, the way that their RPM is dictated is completely different.

The RPM of DC fans is dictated by how much voltage they’re receiving at any given time. The higher the voltage, the higher the RPM. It’s worth noting that because of this system, the fan is always “on” when powered, regardless of how much voltage it receives. This also means that if the received voltage is too low, the fans will stall—keeping it from performing its job at all.

On the other hand, PWM fans draw the same amount of voltage at any given time. Their RPM is instead dictated by the 4th pin, which sets duty cycles based on the information being received through that same pin. While a PWM fan is pretty much always spinning, it’s not always “on.” The duty cycle rapidly flips the fan on and off. A 20% duty cycle would have the fan running at 20%, a 40% duty cycle would run the fan at 40%, and so on.

Because of this, the bearings in PWM fans last much longer, they run quieter, and they’re much more energy efficient than the typical DC fan. It’s also why CPU coolers typically use PWM fans—it allows the computer to  automatically ramp up the fan speed when it’s in need of additional cooling.

When DC Fans Make Sense

But DC fans certainly still have their place—at least for the time being. The manufacturing process for PWM fans is much higher than that of DC fans, directly leading to a higher retail price.

A single, high quality PWM fan can cost as much as $14, while a 3-pack of DC fans will cost around $11. Compatibility is also something to consider—not every case or motherboard offers enough 4-pin connectors to adequately cool a case, leaving DC fans as pretty much the only option.

Even then, there’s no need to stress—in my experience, the difference in performance is minimal.

Robert Brandon

Robert has been building and selling computers as a hobby for a little over 3 years now. When he's not busy immersing himself in his studies, he spends his time reading, writing, and duking it out with others in a wide variety of multiplayer games.

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