How Much Power do Case Fans Use? (Explained)

How Much Power Do Case Fans Use

Do case fans use a lot of power? Do RGB case fans use more power than non-RGB fans? Should you even care about the amount of power that case fans use?

These will be the subjects under investigation today.

We will be talking about fans. Specifically, how much power case fans use. We’ll break it down into different sizes and speeds, and we’ll be sharing a few pro tips with you that you should keep in mind when asking the question “how much power do case fans use?”

So if you’re all set, let’s get into it.

How Much Power do Case Fans Use?

Typically, case fans use anywhere from .06W to 6W, but the actual amount will depend on what fan you’re using, its size, and at what speed it’s running. As an example, a Noctua NF-F12 only uses 0.6W of power, but a Corsair LL120 uses up to 3.96W. So if you’re worried about using too much power, best do your research and add up all the wattage in your computer, then add 25% to make sure your PSU can handle everything spinning up.

The Power Consumption of the Average Case Fan

Your average case fan uses very little power, typically between 1W and 6W. Therefore, many people tend to overlook them in their builds.

While this usually doesn’t cause any problems, it certainly could. Especially if you’re close to maxing out your PSU’s wattage.

If you’re a fan of RGB fans, good news! RGB fans use LEDs that are super efficient, and the amount of power they draw is negligible. So, it won’t make any difference in your overall wattage.

Now, we’d like to share an important tip when building your PC–power management.

It’s important to know the wattage of your fans and to take into account how much extra power it will take when powering everything on.

This is due to a little thing called inrush current. You see, when you start up a fan, or any electronic component for that matter, it creates a peak in the power current to get everything moving. The good news is that the inrush current immediately begins to lessen once the fans start to spin.

After just a few seconds, the fan begins to generate its own power through a process called ‘counter-electromotive force’ that helps stabilize the power flow and maintains the correct operating wattage.

This fact only comes into play when turning on your PC. Once your rig is running, everything stabilizes to normal operating wattages, speeds, and temperatures.

That’s why it’s always a smart idea to tally up your total wattages and add 25% then compare that with your power supply. If your PSU is rated higher than your total wattage, you’re good to go. If it’s lower, you will need to buy a new PSU.

Next, let’s talk about what each size case fan is capable of at varying speeds. We’ll be using the most common sizes in these examples.

80mm Case Fans Wattage

Case fans within the 80mm category are primarily used in small form factor builds. These fans are typically the most power-efficient but, overall, are less efficient in regards to airflow than their 120mm brethren outside of their niche uses.

An 80mm case fan running at 2000 RPM will use roughly 0.9W of power. At 3000 RPM, they’ll use about 1.4W to 1.8W, depending on the model.

This makes them extremely power efficient and allows you to use multiple in your build with little concern for their power requirements.

120mm Case Fans Wattage

120mm case fans are the most common with builders these days. That’s because they hit that sweet spot between airflow and power efficiency.

On average, your typical 120mm case fan will use 3.6W of power during normal operation. But this could go up to or even surpass 6W for models that run at 2000 or more RPM; again, it depends on the brand and model, so know your fans and keep track of your PSU’s available power.

140mm Case Fans Wattage

140mm case fans are another popular choice in larger builds. They are typically quieter and offer a specific aesthetic, especially when you add RGB.

Overall, you can expect around 2W to 6W of power usage at operational speeds between 1000 RPM and 2000 RPM, respectively.

200mm Case Fans Wattage

For the big ‘ol cases, we use big ‘ol case fans–200mm. These are some of the quietest fans, as they only spin at 150 RPM to 1000 RPM. Correspondingly, they do not use as much power as you might expect, despite their size.

For example, a Noctua AF20 only uses 0.96W; that’s surprisingly low! But on the other hand, 200mm case fans can go to the high side of the power range, like the AeroCool Silent Master, which consumes 5.1W.

Like the rest of them, the power used by a 200mm case fan varies wildly depending on make and model, but you can safely assume anywhere between 1W to 6W.

But they are some of the heaviest fans seeing as there is more plastic in the larger fins, so spin-up wattage will be among the highest.

PC Fan

Accounting for Inrush Current

Now, this is where it can get a little tricky. For the sake of this argument, let’s assume you have a 500W PSU. Additionally, let’s also assume your total added wattage is 450W, which leaves 50W left over.

In some instances, the inrush current can be up to, or even over, 300% higher than the listed operating current. So this would mean that a fan rated at 0.08A at 12V would have a normal operating wattage of 0.99W. But taking the startup voltage into account, that same fan would need 0.36A resulting in 4.32W–an increase of 336%.

If you had five of these fans in your PC, then when you start your computer, it will require 21.6W for just a few seconds to get them all going.

That only leaves 28.4W of power remaining in your PSU. And that’s just for the fans. Considering that everything else in your PC also has an inrush current requirement, you’re more than likely going to run into problems such as crashing or worse.

Again, these metrics are only an example, and your mileage will vary, but we can not stress this enough–always add up all of your component’s rated wattage and make sure you have ample wattage left over in your PSU to avoid damaging something in your PC and don’t forget the fans.

How to Determine a Case Fan’s Power Requirement 

Normally, your case fan’s power rating can be found on the manufacturer’s website. It will either show the rating in watts or in amperes or both.

If it’s listed in watts, great! That makes it easier for you to calculate the total power in your build.

If it’s in amperes, that’s ok too, the math is super easy. The formula to figure out your fan’s wattage is as follows.


P is the power in watts, where I is the rated amperes of the fan, and V is current, which is typically 12V for most fans.

Using this formula is simple; just plug in the numbers. Let’s take the Noctua NF-A12X15, for example. It is rated for 0.13A and requires a 12V connection. Multiply 0.13 by 12, and you get P=1.56. So, a Noctua NF-A12X15 uses 1.56 watts.

Now that you know how to determine your case fan’s rated wattage, you can take the total wattage of all your case fans, plus the wattage of all your other components, and match it with your PSU. Easy, right?

In Conclusion

To simplify it all down to the basics, case fans use very little power. But they can all add up, especially when you factor in the inrush current requirement.

We don’t mean to sound like a broken record here, but it’s important to make sure your PSU has more power than you’re using. If you’re getting close to your power supply’s wattage limit, instead of looking for power-efficient fans, you should just buy a stronger PSU.

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About Kasimir Wera 25 Articles
Kasimir has been fascinated by technology from a young age. It started when he got a Nintendo 64 for his 7th birthday and took it apart to see what was inside. Now, many years later, that fascination with gaming and technology has only grown with the technological boom he grew up in. Over the years, he has built, upgraded, and repaired many PCs for himself, his family, and his friends. These days, Kasimir lives his best life writing, tinkering with computers, and playing video games with his daughter and friends.

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