Why is Avast Taking so Much CPU [Avast Performance Guide]

Avast is one of the top free antivirus software you can get. However, like many antivirus programs, Avast can be resource-intensive. You might find yourself asking, ‘Why is Avast Taking so Much CPU?’ If you too see Avast using too much of your CPU, then you have come to the right place.

The best things to do when Avast CPU usage is high is to change Avast settings to reduce the number of background scans it does. Other things that can help are reinstalling Avast Cleanup and to disable Avast screensaver scan. 

Getting your PC to run like it should can be a hassle, but we are here to help. In this article, we will walk you though all the different things that cause Avast to slow down. Also, we will provide step-by-step instructions that you can follow to make Avast run better.

Why is Avast Taking so Much CPU?

Antiviruses are intrinsically resource-heavy. The Avast service provides several different operations such as virus scanning, file clean up, and background scanning. While these processes are helpful, they use a lot of your PC’s resources to function.

When you see in the task manager that your PC usage is high, you might notice that ‘avastsvc.exe’ is used the most. You will also see ntoskrnl.exe using a lot of RAM. Avast can use more CPU than it needs to if the system settings aren’t configured correctly. Also, this can happen if there are issues with your Windows Registry.

Method 1: Reinstall Avast Cleanup

One of the things that the Avast antivirus package provides is a real-time threat protection service called Avast Cleanup.

This service runs in real-time so that it can free up some resources for other background apps. Remember, any real-time service is going to be heavy on CPU usage.

Step 1: Open Avast from the System Tray

Step 2: Navigate to Settings

Step 3: Go Protection

Step 4: Click the Core Shields subsection

Step 5: Select the shields you want to remove

Step 6: Click the right arrow menu

Step 7: Uninstall them from the option

Step 8: Restart your PC.

Hopefully that helped your Avast CPU usage. Now that your PC is up and running again, check the task manager to confirm that your CPU usage has gone down to normal levels. If it hasn’t, you may just need to change your scan frequency.

Sometimes, the problem is with Avast behavior shield. Try uninstalling that to see if it fixes your Avast CPU usage problem. If that resolved the problem, but you want to keep Avast Behavior Shield, then just try to reinstall it again.

If you reinstall it and Avast CPU usage is too high again, then you know there is nothing wrong with Avast and it’s just your computer not able to keep up with the demand.

If you reinstall Avast Behavior Shield and your Avast CPU usage is still low, then you know the problem is not with your computer’s performance, but it was rather a corrupted file that was fixed by the reinstall.

If this doesn’t help at all, you can also try reducing the scan frequency to reduce load on the CPU.

Method 2: Change Scan Frequency

Avast runs background scans to help prevent your PC device from getting a virus infection. So, if there is a noticeable spike in your CPUs usage caused by the Avast service, it might just be because of a background check run.

You can change the scan frequency from the command prompt by following these steps:

Open an elevated command prompt. 

Step 1: Press Win + R to open Run dialogue

Step 2: Type cmd, and hold CTRL and SHIFT, then press enter
FYI: When you hold CTRL and SHIFT before running a command from the run dialog, it will run the command in administrator mode. 

Step 3: Enter the following command into the command prompt:

cd C:\ProgramData\AVAST Software\Avast

Step 4: Enter the following command in the command prompt:


Step 5: Press Enter

This will open Avast’s configuration file in notepad with administrative privileges. This will allow you to edit the Avast system files where you normally wouldn’t be able to. Proceed with caution.

Step 4: Add the following line at the bottom of the file:

[GrimeFighter] : ScanFrequency=999

Step 5: Click File, then Save, or hold CTRL and press S on your keyboard

Step 6: Restart your PC

Doing this will stop the real-time checks and reduce it to just every so often. While this may cause some security concerns, it will definitely reduce the CPU usage.

Method 3: Disable Avast Screensaver Scan

At times, Avast’s screensaver scan continues to scan even when the screensaver has stopped. This isn’t too common, but it does happen. When this rare case does crop up, it’s often the primary reason that the Avast CPU usage is too high

The settings for this type of scan is not accessible in the Avast interface, so this is how to solve this problem:

Step 1: Right click on any file and choose ‘Scan with Avast’

Step 2: Wait for the scan result window will show up, it will show a list of running scans on your system

Step 3: Go to the Avast screensaver scan and click Stop

Step 4: Close the window and see if your CPU usage has gone back to normal.

If that didn’t resolve the issue, then you may have to update or repair your Avast installation.

Method 4: Update The Avast Application

Sometimes, something as simple as outdated software could be robbing your PC of its performance. If older, buggy versions of software become unresponsive, it could drastically increase your CPU load. So, it’s always good to keep your virus definitions and your antivirus software itself up to date.

To update Avast Antivirus and it’s virus definitions, perform the following:

Step 1: Open Avast from the system tray icon

Step 2: In the Update tab, take note of the current version of Avast and the virus definitions

Step 3: Click ‘Update’ next to both

A lot of users have reported that updating Avast solved issues that they were having with the Avast service using high CPU and other resources.

If updating doesn’t solve the problem, you may need to reset Avast.

Method 5: Reset Avast

If you are already on the latest version of your software, or you were able to update and it still didn’t help, there could be some corrupted data files that are causing high CPU utilization. You can try to repair the software to fix this problem.

Here are the steps that you need to take to repair Avast.

Step 1: Open the Control Panel and choose Programs and features

Step 2: In the list of installed applications find Avast and click on ‘Uninstall/Change’

Step 3: Click on Change.

Step 4: Select Repair.

Step 5: Wait for Avast to finish the repair

Step 6: Restart your PC and check if Avast CPU usage is lower


Avast is no doubt one of the most widely used free antivirus softwares out there. But it does command some pretty high CPU resources sometimes. But, now that you know how to fix Avast service high CPU usage error using the solutions above, you have a better shot of working out the problem.

Reducing the frequency of background scanning is one of the best things you can do when Avast CPU usage is too high. If that doesn’t work, you can try to disable the Avast screensaver scan.

Sometimes Avast just needs to be reset or reinstalled. If you are still having the same problem after that, we recommend that you uninstall and reinstall Avast Cleanup before you do the same to Avast entirely. Sometimes Avast Cleanup has problems with it’s files and needs to be reset.

Getting your PC at it’s best is always a challenge. We hope this article helped you speed up Avast and reduce Avast CPU usage.