Why Does CPU Heat Up? (13 Reasons & Fixes)

By Dominic Chooper on December 12, 2022

Since, your CPU is a high heat generating component in your computer. It stays hot while it is switched on and will only cool down when it is either being used in low power mode or is in sleep mode.

This happens because your CPU uses very less power or is not working at all. Fortunately, this heat is often harmless to your computer, as it is within normal range for working systems.

In some cases, your CPU might become very hot and you are left wondering why the CPU is heating up. Read on to know some common reasons and solutions for why your CPU is heating up.

How Fast Does a CPU Heat up?

Why Does CPU Heat Up

It takes just a few minutes for your CPU to heat up and reach temperatures ranging from 60-70 °C.

Without a proper cooling mechanism your CPU will take 30 seconds after starting up to reach this temperature range. CPUs are designed to work efficiently even at such high temperatures.

Other than its design, your CPU also heats up rapidly due to processes like turbo boost and hyperthreading.

Applications that are CPU resource-intensive or demand a lot of real-time processing also increase your system’s temperature, as they require your CPU to work harder and faster.

Overheating CPU Symptoms

The most obvious sign of your CPU overheating is change in room temperature. When you are using your computer and it starts overheating you feel the rise in temperature, as such high temperatures in such close proximity do not go unnoticed. Other symptoms of your CPU overheating are:

Random shutdowns:

When your CPU overheats and it is unable to cool down at all, your system automatically shuts down. This process is known as hard crashing and is oftentimes used as a last resort by your computer in order to cool down.

Since, your processor chip might melt if it continues to heat up. This is a clear symptom of overheating because CPU temperature is close to reaching its maximum threshold.

Loud fans:

Fans in your computer generally run at a suitable speed and generate a barely audible hum, unless you have configured them to work at their highest setting, which produces a louder whirring noise.

However, if your CPU starts overheating, its fan followed by all other system fans will automatically increase their speed to lower your system’s temperature.

When all fans in your computer are functioning at their highest speed, they make a lot of noise. As they are trying to maintain continuous airflow, which might work to reduce CPU temperature gradually.


Your CPU’s ability to function normally gets affected once it starts overheating, which causes minor errors. These errors start off as small glitches which often rectify themselves in a few seconds.

Some such common errors are disappearance of your cursor, unregistered clicks and hiccups in your sound system.

These glitches continue persisting and over time increase in intensity if you do not resolve your system’s overheating problem.

Sluggish system:

There are numerous factors which force your computer to function slowly. For example, if you do not turn off your system even for a day, its performance starts feeling sluggish.

Overheating plays a major role in making your computer sluggish, but chances are you will overlook overheating when troubleshooting, thinking a more complex issue is to blame.

When other internal components of your computer start heating up due to your CPU overheating, it starts affecting overall computer performance.

Repeated CPU throttling:

CPU throttling refers to slowing down of your computer immediately after your CPU temperature reaches its maximum threshold.

This guarantees that your CPU is overheating, CPU throttling occurs to prevent your CPU or entire computer from getting severely damaged.

13 Reasons Why CPU Heats up

CPUs start generating heat when they are connected to a power outlet, as they convert electrical energy to thermal energy.

Your CPU, most likely contains more than a few billion switches or transistors that control the flow of electricity.

These switches are placed throughout your processor and therefore some energy is lost and some gets converted to heat.

Thermodynamics, entropy and Joule’s law explain the primary reasons why the CPU heats up immediately after being powered on every single time.

1. Thermodynamics and Entropy

According to thermodynamics’ first law, energy cannot be created or destroyed, it only converts to other forms.

Even energy which we assume is lost is not actually lost but gets converted to a form which we do not take into consideration. All forms of energy, be it thermal, electrical, mechanical or kinetic follow this law.

Entropy (energy transfer) is explained in the second law of thermodynamics. According to it, in any system where energy is being input, if energy transfer remains constant, heat transfer is necessary.

Simply put, if energy is being converted from one form to another in a system where there is a constant input of energy, then energy that we assume to be lost is actually thermal or heat energy.

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In terms of computers, if your CPU does not completely utilize electrical energy passing through your system, this energy will be lost/wasted as it gets converted to heat energy.

Therefore, it is necessary for your CPU and computer to generate heat whenever connected to a battery or power source.

As, it prevents energy from getting stored in other components in a harmful manner. All extra energy gets removed from your system in a safe way as heat.

If your computer does not follow these laws of thermodynamics, electrical energy will get stored in its components and it will eventually disintegrate, damaging its surroundings.

Fortunately, in reality your CPU will not get fried electrically, since it is capable of releasing all the heat, it generates.


If your CPU is not heating up, then you need to get it inspected by an expert technician, because zero heat generation indicates that electrical energy is getting trapped in either CPU or other components of your system.

2. Joule’s Law

According to Joule’s law, electrical energy in a circuit will convert to heat energy only when it faces any resistance or obstacles. CPUs in general are not created with resistors and also do not experience resistance from cables and wires.

IC (Integrated Circuits) or chipset of your CPU is made up of transistors, diodes, and semiconductors.

This offers some resistance which eventually leads to some loss of electrical energy and energy required for conversion from one form to another.

Generally, superconductors are the only components that offer no resistance to electricity, however when used in CPUs they offer some resistance as its conductivity is fairly low.

Transistors in your CPU’s chipset are used as switches, as they allow or prevent electricity from flowing through them.

This is how your CPU’s components communicate amongst themselves, and fulfill input and output requirements while creating some resistance.

Therefore, when internal components of your CPU are not using all of the electrical energy passing through them, heat is generated while creating resistance.


It is necessary to allow the CPU to function properly, therefore, it should be allowed to heat up to some extent. Only then should advanced cooling measures like external cooling systems be set up.

3. TDP (Thermal Design Power)

Modern CPUs generate a lot of heat, as their computing speed and abilities have increased. TDP, also known as thermal design point at times, is a value indicating how much heat your system’s CPU can bear while remaining functional.

It is the highest point of heat, according to which your CPU’s cooling system is designed. Regardless of its workload, if a CPU reaches this point, its cooling system is equipped to handle quick cooling, while ensuring your system is not damaged in any way.

A CPU in 1978 had a TDP of 1W, however, today CPUs generally have 95W as their maximum TDP.

This is not even a high-end CPUs TDP value, as they now go up to 400W. A TDP value does not indicate that a computer draws this amount of energy at all times.

However, it tells the amount of power a CPU is capable of using while working at maximum load, without overheating.

Similarly, throttle temperature for modern CPUs lies between 90 °C to 100 °C. Beyond 100 °C, CPU components might get damaged due to heat.

Even if it does not happen immediately, they might melt or fry themselves when overheating occurs repeatedly.

During throttling your CPU will automatically end multiple processes and drastically lower its electrical consumption right away.

You might be alarmed as throttling may seem like your CPU is dying, however, it is just protecting itself and allowing cooling components to carry out their task quickly.


Your CPU is designed to protect itself, therefore you must not panic when it throttles and give it time to cool down.

Bear in mind that shutting down your CPU or immediately turning off power supply, does not help with rapid cooling, because your computer’s fans will stop working as soon as your computer is powered off.

4. Number of Transistors

Previously, CPUs had less than 30,000 transistors, however now this number has increased significantly. Even simple computers used for performing basic tasks are equipped with more than a few billion transistors.

A CPU’s logic gates are controlled using these transistors, as they switch on and off to regulate flow of electricity according to tasks assigned to it.

A lot of heat is generated with this significant increase in the number of transistors, and overall speed at which they have to function.

Additionally, stopping and allowing i.e., switching on and off of electrical flow generates significant heat as well.

It is necessary that transistors function in this manner, because otherwise, computers cannot function or carry out any computational tasks.


Do not overwork your computer. Take breaks while working in order to allow your computer time to relax and cool down as well.

Put it in sleep mode or customize low power settings so that it does not have to send a lot of information to peripherals including your system’s monitor.

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This way, electrical consumption is lowered when you are not actively using your computer. Also do this when you do not want to turn off your computer, to allow any processes to run in the background.

5. Clock Speed

During the late 1970s CPU clock speeds ranged between 0.005 to 0.001 GHz. Now, CPU clock rate is around 4.0 GHz which can also be increased by another 1 GHz through turbo boost.

Overclocking or turbo boost is used to modify your CPU’s settings, forcing it to perform close to 100% of its capacity. Consequently, an overclocked CPU is able to operate at 5 GHz speed.

This increase in speed and computing power indicates an increase in the total amount of electricity it draws.

Not only your CPU but other components in your computer also use more power with increase in processing speed. Naturally, with an increase in electrical consumption the amount of heat generated also increases.


Heat generated by a system while processing quickly is completely normal and you should not worry about it. However, overclocking is not generally preferred as it increases chances of damaging a CPU.

If you do not have in-depth knowledge of manually overclocking, you must not do it, since it is a risky and complex process.

You must not start this process unless you know all its steps and how to rectify if anything goes wrong.

You also need to know all details of your processor as well as the extent to which overclocking is safe. If you overclock too much, chances are your system will crash due to permanent hardware damage.

Also, overclocking is not always beneficial, even if you know how to do it properly. You can increase your CPU’s speed by one or two units if fast processing is your end goal.

However, overclocking to get maximum results from your CPU is not ideal, as it harms hardware.

Overclocking voids your warranty, so do not attempt it before your warranty expires.

Moreover, overclocking might not be able to increase your computer’s processing speed all that much, because this speed is dependent not only on CPU, but other components as well.

Graphics, hard drive and RAM cannot perform at this same speed and ultimately result in bottlenecks.

6. CPU Bus Speed

Four to five decades ago bus speeds were 4.77 MHz, now this value has increased manifold and bus speed for even low-end systems is around 3000 MHz.

A CPU’s bus speed increases its processing speed, consequently generating more heat.


Ensure your CPU’s cooling systems are in place and working efficiently, as all components generating heat at the same time will require a powerful cooling system to maintain normal temperature range for optimal CPU functioning.

7. Integrated Graphics

GPUs or graphics cards are available in two types, a dedicated separate unit and one which is built into your CPU. This in-built graphics card might seem like a better option as it is less expensive.

Since, a dedicated GPU is expensive and also requires additional memory. Keep in mind that the total amount of heat generated by a CPU with integrated graphics card increases significantly, but is nowhere close to heat generated by a dedicated GPU.


For an integrated graphics system, it is necessary to have a bigger fan installed near your CPU.

Also, your CPU heatsink must be bigger in size to absorb more heat quickly. Otherwise, your CPU might get damaged due to excessive heat accumulation and lead to system failure.

8. CPU’s Small Size

A CPU chipset is a very small unit in terms of physical size. When it heats up, this size proves to be a disadvantage, as less surface area makes it difficult for heat to be released quickly.


A heatsink is useful as it radiates heat and lowers CPU temperature. But a fan also needs to be mounted close to your CPU, in your computer frame.

When purchasing custom-built CPUs or building one on your own, ensure a fan is placed close to your CPU and heatsink.

Also, remaining fans must be placed strategically ensuring all components are able to cool down while increasing air flow through vents.

9. Dust Accumulation

One of the most common reasons for your CPU heating up is dust accumulation. While the CPU does generate heat by itself, it is designed and outfitted to cool down by itself.

However, dust accumulation affects your CPU’s abilities to cool down by itself, as it traps heat by covering all surfaces used for releasing heat.


The first step to having a clean computer is preventing dust from entering. This can be accomplished easily by installing air filters over all vents.

These filters do not slow down or obstruct your CPU from cooling down. But they do prevent bigger dust particles from entering your computer, keeping it comparatively clean.

You need to remove and clean these filters every week to ensure they are not completely covered in dust and consequently blocking air flow.

The next step is opening up your CPU’s case and cleaning it thoroughly from inside. This can be done once every one or two months, if you are using filters on your CPU vents.

Things you need to clean your CPU case are paper towels, cotton swabs, isopropyl alcohol and a microfiber cloth.

Do not spray alcohol on any components to clean them as it might harm them. Start by spraying it on paper towels or a microfiber cloth and wipe using these dampened surfaces only.

Cotton swabs must be used to access crevices, clean up corners, and also clean any delicate parts.

10. Dry or Worn-out Thermal Paste

Thermal paste, also known as CPU paste or thermal gel, allows transportation of heat from your CPU to heatsink.

The CPU and heatsink are next to each other, but there are still some gaps where air prevents heat release. Since, air prevents heat release because of its poor conducting nature. S

o, you must use thermal paste to bridge any gaps where air pockets remain.

It takes most thermal paste products three to five years to dry up before they need to be replaced.


If you carefully observe your CPU, you will notice right away when thermal paste around your CPU needs to be changed.

Your CPU temperature increases easily and when CPU resource-intensive applications are running it might also result in overheating.

There are three types of thermal paste, namely, metal-based, ceramic-based, and carbon-based. Read up about thermal paste to decide which type is best suited for your computer’s needs.

Start by removing your CPU and clean up debris or older layers of thermal paste. Thermal paste has a special removal kit which makes it easier to remove dried up residue.

Clean up your CPU and ensure all surfaces are dry before applying thermal paste. When applying, do not let thermal paste stick to any other components or CPU case’s inner walls. Clean using its removal kit, in case it spills out.

11. Fans – Broken, Dirty or Malfunctioning

Any problems with your computer’s fans increase heat and make it sound like you are sitting next to a loud engine.

Noisy fans are a result of dirt accumulation or some other malfunction. If you have a water-based cooling system for your computer, you need not care about these fans.

If not, it is necessary to resolve any problems related to these fans immediately as they are necessary for keeping your computer alive and healthy.


You need to start by determining a reason why your computer’s fans are not working as they should be. If you have recently cleaned your system, both inside and out dust accumulation can be crossed out as a reason.

If your computer has not been cleaned for a month or two, try cleaning it up before restarting it.

If your fans are still making noise try moving your computer to a cooler place with better airflow. Do not place it close to a wall or other objects which block air flow.

Check your system’s BIOS settings for fan speeds and efficiency or use other dedicated tools to detect if fans are slowing down or speeding up unusually. Monitor and change settings to optimize these functions of these fans.

If your CPU case still has extra space, you can install a new fan.

Configure all fans to ensure they are moving in the same direction. Otherwise, it will only increase heat accumulation as they might be blowing air against each other.

12. Virus and Malware

A virus, malware or worm can lead your computer to produce extra heat as it causes processes to stop working properly.

While some viruses will block programs from operating or opening up, there are some which make them work harder.

In order to keep up with instructions being given by these applications it is necessary for your processor to work faster and harder, contributing to excessive heat production.

Your computer might shut down to keep itself safe, if a virus makes it perform at a 100% of its ability.


If you have an antivirus or anti-malware application, update it immediately and start a scan. Do not use any other applications while scanning to prevent loss of work and overheating of your CPU.

Delete all files marked as infected as you can download uninfected copies later on. You might want to make an additional copy of irreplaceable data files and upload them to a cloud.

If you do not have antivirus or anti-malware software on your computer, install it immediately, even a free trial version is enough to get rid of a virus that is preventing your computer from operating properly.

Perform weekly or monthly scans to ensure your system does not get infected again.

13. Hardware and Software Compatibility

Some applications might be too resource-intensive for your CPU causing it to overwork and produce excessive heat.


Always check hardware specifications before installing new software/applications to your system.


If you have purchased your CPU from a reliable brand, you need not worry about why the CPU heats up, as this heat is not harmful and will dissipate.

However, if you have built your own CPU or purchased a custom-built one, you need to check for overclocking as it might be contributing to increased temperatures.