Monitoring options give us an easy way to quickly assess whenever something feels odd or different from the way our PC normally operates. This is why it is such an inconvenience when CPU usage statistics occasionally show conflicting data, where the computer still feels sluggish despite the monitoring app indicating a low percentage value. So, what to do when the computer is slow despite low CPU usage?
To fix a slow computer during low CPU usage, keep your CPU cool, check your RAM usage and clean the PC with antivirus software. A slow computer can be an indicator of a hidden, perhaps more malicious, program that hides its activity from most standard monitoring applications.
So would removing the bad software fix the issue? How exactly do we know which component is affecting the computer? And are we even certain about the low values shown? All answers to that and more are below.
Why Can Computers Be Slow Despite Low CPU Usage?
1. Your CPU is Getting Too Hot
Your computer may be scaling down its usage level because it is already at its temperature limit. Thermal throttling is a phenomenon in which a component goes above its designed thermal operational limits, also known as its TJ max. When this happens, the system automatically brings down its usage level to protect the component from completely melting down.
In other words, your CPU is deliberately slowing itself down, therefore lowering its use percentage, whenever it becomes too hot for its normal operations.
As for why it is getting too hot, there are several typical scenarios to consider:
- Thermal control is inefficient. The cooling solution installed on the CPU may just be unable to handle the CPU as it ramps up its performance level. Or, the PC case itself tends to accumulate or trap significant levels of heat.
- The cooler is improperly installed in some way. Users might have forgotten to peel off the protective sticker on the copper base plate before installing it on the motherboard.
- Inadequate thermal paste – while too much thermal paste may cause serious socket obstruction issues, too little means the heat transfer from the CPU’s IHS to the cooler base plate is not optimized enough.
- Faulty CPU – the CPU may have an internal hardware-based issue that prevents it from properly dissipating in any effective way. Though this issue usually becomes quite apparent by just checking default temperature values in BIOS.
2. Your PC Doesn’t Have Enough RAM
When the PC runs out of available memory, it can no longer fetch pre-loaded data as quickly as it normally can. When this occurs, the computer resorts to using the Page File, an emergency backup that uses part of your primary storage drive (boot drive) as RAM. Using a storage drive to do the job of faster RAM means that at this point, the user will now feel slowdowns in the system.
For faster modern SSDs at least, this will only take the form of microstutters. But for PCs that are still using HDDs as traditional boot drives, the experience can be as excruciating as a few seconds of constant delay between different tasks.
And speaking of HDDs…
3. You Are Using a Hard Disk Drive for your OS
When compared to modern systems at least, hard disk drives used as boot drives or software drives just feel a lot more sluggish regardless of CPU usage. This is all due to the simple differences in data transfer speeds of modern SSDs to HDDs today. The difference is immediately apparent even as you start the system. SSDs take only several seconds to boot, while HDDs take almost a minute or two.
When launching applications, the same slowness is also felt. Whereas modern SSDs feel very responsive, HDDs take a while to launch programs and process commands. The delays are not as problematic as dealing with full RAM, but the half-seconds to one or two seconds of delay definitely add up as the day goes by.
4. Your PC has Malware
If you still experience slowdowns despite using an SSD as a boot drive, having plenty of RAM, using efficient cooling, and low CPU usage, then the last culprit is hidden malicious software. Depending on the objective of the creator, these suspicious programs creep inside your PC and use its resources behind the scenes.
What’s even more sinister, is that modern iterations of these viruses and malware are built so that they would suddenly go inert and hide when monitoring software is launched to attempt to detect them. The most popular example of such is Trojan Bitcoin miners, malware that passively uses your PC as a cryptomining slave while you’re not paying attention. 
Once the user feels the slowdown, they will be urged to open the Task Manager. But once they do, the malware simply stops its work, fooling the user into thinking that nothing is wrong since the CPU usage is low. It will then come back to grind your PC’s components again once you look away.
How to Fix Slow Computer When CPU Usage is Low?
1. Keep Your CPU Cool
The basic target is to go 15 degrees Celsius below the CPU’s TJ max. Even better, you should go at least 25 degrees lower to prevent all possibility of hardware degradation due to temperature. On most computers, this means keeping your CPU temperatures at least 84 degrees Celsius, and optimally 75 degrees.
To achieve such numbers, we only need to do the reverse of the reasons why it gets hot:
- Use a better cooler. if the CPU goes above my recommended temperatures, then it may be time to buy a better cooling solution. Maybe you have an overclocked Intel Core i5 12600K that desperately needs a 240-rad AIO, or your Ryzen 5 5600X requires a nice, tower cooler upgrade before letting loose all its power.
- Be sure that the cooler is properly installed. use the right amount of thermal paste, don’t forget to peel off the base plate sticker, install the tower cooler fan and exhaust fan with the same wind direction, and orient your AIO pumps in the right direction.
- Maintain good airflow. your PC should let fresh, cool air at constant times, and keep it flowing in just one uniform direction. Case fans should also be of good quality for this.
- Clean dust from PC at regular intervals. compressed-air cans are typically the best way to do this. Push dust away from the heatsinks and fans at least every two weeks, or every month. Don’t let dust accumulate until it turns into dust bunnies, as it could even potentially damage your system.
2. Keep Your Available RAM Adequate
Always remember to check your RAM usage regularly, and to close down apps or tabs that you may no longer be actively using. You can also opt not to use RAM-intensive applications, or reserve such software only when you need them.
Better yet, invest in a fresh, new pair of memory kits, and upgrade the capacity of your PC’s RAM. You can either popular extra unused DIMM slots, replace the RAM you are already using, or add another stick of RAM if you are only using one stick (single-channel).
Remember, the cost-per-capacity sweet spot today is 16GB (x2 8GB or x4 4GB), which allows perfect breathing room for all modern apps, including tab-heavy web browsers.
3. Be Smart With Your Web Browsing
Don’t be tempted to enter suspicious sites, and don’t click on links unless you are absolutely certain you trust the source. A dominant number of viruses and malware today can only infect when the trigger is pulled. If you play it smart (or safe), and be constantly alert to these things, you usually never have to worry about hidden programs messing with your CPU usage ever again.
4. Clean Your PC With a Reliable Anti-Virus Software
This is only for the unfortunate people who already have malware in their system without their knowledge. Do not forget, you are only going to do this once, in practice. Maintaining tip no. 3 (being smart with web browsing) is a thousand times better than getting malware or any kind of virus in the first place.
As for our recommendations, go for either Kaspersky or Malwarebytes. Then default to fully-kitted Windows Defender for first-aid solutions.
How Much CPU Usage is Normal?
Normal CPU usage depends on a lot of factors, but mainly what your CPU is made of and what you are doing at the moment. Modern four-core eight-thread CPUs, for example, may simply trot at a leisurely 20-30% when browsing the internet, or chill down to 12% or 15% when using basic office applications.
Certain tasks, such as graphics rendering, or video editing, will use all available power of your CPU. This means that it will push to 90% or even 100%. It can also jump quite high when playing triple-A games at 1080p, at least 50%, or even 80%+ when the game is particularly CPU-intensive.
One thing is universal, though. With an adequately modern CPU (at least four-core, 8th Gen Intel Core or 1st Gen AMD Ryzen), when your PC is idling, it should always fall somewhere near 10% or lower. Anything much higher means that something else is going on behind the scenes.