The conventional advice about PSUs is to go over what your system needs.
Many experts recommend buying a 550-watt unit for a PC that only uses 400 watts.
What happens if you don’t listen to that advice?
What if you go lower than the system’s maximum usage?
In this article, we’ll tell you the answer.
We’ll review all the scenarios that may happen if you have a weak power supply.
What Happens If Your Power Supply Is Too Weak? (7 Things)
If your power supply doesn’t provide enough wattage, you’ll experience unexpected shutdowns, especially when you game or perform GPU-intensive tasks.
Other less severe problems include blue screens, system freezes, program crashes, and lower performance.
In rare cases, you may not be able to boot or even turn on your computer on with a weak PSU.
Generally, the best way to avoid these shutdowns is to replace your current PSU with a higher-capacity one.
You can also reduce your computer’s power consumption by disconnecting extra hard drives or PCI devices.
Alternatively, you can avoid putting your GPU under full load (e.g., by lowering your game settings) so it doesn’t draw as much power.
The exact response of a computer to being underpowered depends on its hardware and software configuration.
Let’s discuss the specifics of the potential issues caused by a weak power supply and how you can fix them.
1. Unexpected Shutdowns
Computer power usage isn’t linear; it has sudden spikes that exceed the average usage by 15 to 20 percent.
For example, if your average power usage sits at around 400 watts, your computer could draw as much as 480 watts in some instances.
If you have a 450-watt PSU, the PSU will shut down the computer when usage spikes above its capacity to protect the components.
That’s especially the case when you game, edit videos, or perform other GPU-intensive activities, as the GPU is the most power-hungry component in your computer.
Note: Low-quality power supplies may not have an under-volting protection circuit.
Therefore, they may not shut down the computer when the power draw exceeds their capacity, which could damage your parts.
2. Random Restarts
There are so many reasons for random restarts that listing all of them requires a separate article.
However, you most likely have a hardware problem when your computer restarts out of the blue.
Power issues are one of the main culprits.
Your motherboard or CPU is receiving too little (or too much) power, so either one could restart the computer to protect itself, hoping the issue won’t occur again.
One of the capacitors in the PSU may have reached the end of its life.
Before deciding the PSU is the cause, eliminate other common reasons for random restarts.
Replace your hard drive and RAM with reliable replacements.
If the issue persists, consider a replacement PSU.
3. Blue Screens
When a non-critical component gets underpowered, it causes a blue screen instead of immediately shutting down the system.
Blue screens are slightly harder to tie to a power supply issue as you have to discover the link indirectly.
When your system throws a blue screen, it logs the details in a dump file on your boot drive.
You can view the logs using the right software: BlueScreenView.
Once you download and install the program, you can view all the dump files on your system ordered by crash time.
Google the bug check code and driver file name to determine which component malfunctioned.
From there, you should identify the root cause of the issue and see if it has anything to do with your PSU being weak.
4. System Freezes
System freezes caused by underpowered motherboards and GPUs are possible.
However, freezes are more often caused by software than hardware.
When your computer stops working, see if your caps lock indicator or mouse light works.
If so, you’re dealing with a software issue.
Otherwise, you need to check your hardware.
USB conflicts and malfunctions are very common.
Restart your computer and plug your mouse into one of the USB ports.
After a while, connect the keyboard using the same port.
Test all the USB ports in this fashion to see if you find a malfunctioning one.
If your motherboard has onboard WiFi, disconnect it and use an ethernet connection.
Then disconnect your GPU and connect your monitor using the onboard graphic if your CPU has one.
5. Program Crashes
If you notice one or several programs regularly crash on your computer, there’s a chance that your PSU is weak.
Admittedly, the causality chain is a bit long, but it’s still possible.
For example, your CPU doesn’t receive all the power it requires, so it limits its voltage and frequency to decrease its power consumption.
As a result, it crashes when you open Photoshop, Matlab, or another CPU-intensive program.
The same situation can happen to the graphics card.
Like a blue screen, Windows logs program crash details and lets you view them using the built-in Event Viewer utility.
Search Event Viewer in your Start menu or navigate to Control Panel > Administrative Tools > Event Viewer.
Under Windows Logs > Application, find the error message and google it to identify the issue.
You can determine whether the problem is related to your power supply with a little digging online.
Note: Sometimes, you may get an error message from a game or program that points to the power supply issue.
However, you won’t get this type of error message from all apps and games.
6. Reduced Performance
Sometimes, your PC parts react to being underpowered by reducing their performance.
Your CPU might draw less power and run at a lower frequency.
For example, your 3.8 GHz CPU may operate at 1 GHz, which translates into lower FPS in games, longer render times, and frequent lags.
Lower graphics performance, such as reduced resolution or display problems, is also common.
If you’ve ruled out other causes and suspect your PSU, replace it with a reliable one to see if the problem disappears.
If your performance issues are only CPU-related, you should have a technician also test your motherboard.
7. Failure To Boot
Finally, your computer might be unable to boot if your PSU is too weak.
Depending on your hardware, your system needs between 50 and 150 watts to turn on and load your operating system.
If the PSU can’t provide that wattage, your system won’t operate.
This problem is characterized by your computer shutting down a short while after being switched on, usually before loading Windows.
That’s because power usage is very limited after you turn the computer on but increases as the graphical user interface loads.
If you can’t turn on your computer at all, chances are your PSU is completely dead.
However, before reaching that conclusion, you must rule out a few other causes.
For example, you must ensure your RAM and CPU are functioning properly.
How to Tell If Your Power Supply Is Overloaded
A power supply is responsible for converting the 110 or 220 volt AC power from the wall to 12 volt DC that your components can use.
Some components may need 5-volt and 3-volt power, which the PSU generates.
To see if your PSU has enough juice for your parts, you need to add up the consumption of individual components and compare it with your PSU’s capacity.
Your graphics card and CPU consume the most power.
Their consumption varies across brands and models.
In contrast, motherboards, RAM sticks, and storage devices use relatively the same amount of energy.
So, the most basic approach is to add your CPU and GPU’s thermal design power (TDP).
Then add 150 to 200 watts for your motherboard, RAM sticks, and storage.
Each RAM stick generally consumes about 3 watts, while SSDs and hard drives use around 5 and 10 watts, respectively.
ATX motherboards can consume up to 150 watts, but they usually don’t exceed 100.
Smaller motherboards tend to require less power.
Once you have the final tally, compare it with the output power on your PSU.
If the difference is more than 10 percent, you may experience frequent shutdowns and performance issues.
However, smaller differences are less likely to cause trouble because your parts won’t always consume the maximum advertised TDP.
Note: If you overclock your CPU (and GPU), add 200 to 300 watts to your power consumption.
Moreover, you should also consider component aging.
PSUs tend to lose a few percent of their capacity after a few years.
Although the difference isn’t considerable, it can impact your setup if you don’t include a large headroom when buying your PSU.
Let’s consider a hypothetical setup to help you understand the details.
Suppose you have the following computer:
- CPU: Intel Core i5 11600K (TDP = 125 watts)
- GPU: Nvidia RTX 3060 (TDP = 170 watts)
- Motherboard: PRIME Z590-A
- RAM: 2×8 GB DDR4
- Storage: 1TB WD Blue SN550 M.2 NVMe SSD
This setup requires between 340 to 370 watts to work.
In all likelihood, you can get away with a 350-watt power supply.
However, you should buy a 450-watt unit to avoid headaches down the line.
If you find these calculations confusing, you can use a PSU calculator to remove all the hassle.
Outerversion has a comprehensive calculator that lets you pick your CPU and GPU models and specify their utilization.
You can also input your other components, including the RAM, storage, and motherboard.
The expert tab gives you much more control over the details.
You can include up to two graphics cards, multiple PCIe expansion cards, fans, and peripherals in your calculations.
If you’re an overclocker, you can specify chip utilization, frequency, and voltage.
Once you’ve input all the information, click the calculate button to get a recommendation on the power supply you should have for your system.
Admittedly, all the controls and knobs can get a bit overwhelming.
The last one is especially user-friendly and easy to use.
Measuring Actual Usage
All of the calculations we’ve done so far are estimates.
Your exact power consumption varies second by second, depending on your CPU and GPU load.
Playing games requires more power than word processing, which also needs more power than keeping your computer idle.
If you’re interested in knowing the exact amount of power your computer uses, you need a power meter.
A power meter is a small device that sits between your outlet and power bar, allowing you to measure the wattage going through the outlet each second.
You can buy a cheap meter for less than $15 on Amazon.
More expensive options come with built-in memory, extension cords, and advanced features for debugging electrical circuits.
How Many Watts Do You Really Need?
As you can see, estimating the wattage you’ll need is easy.
Calculating an exact number isn’t that straightforward, though.
The most reliable approach is to measure actual usage in different scenarios with different pieces of hardware.
We’ll leave you with this YouTube video from Gamers Nexus that does exactly that.
If you’re not interested in the testing methodology and the nuances of hardware differences, you can skip the first six minutes.
Choosing A Power Supply
Power supply specs are notoriously misleading.
Unfortunately, manufacturers sometimes trick buyers into buying subpar products.
To help you avoid shady products, we’ll cover the most important specs to consider when choosing your PSU.
There are two ways to express a power supply’s capacity: peak wattage and continuous wattage.
Carefully read the PSU’s specs to see which number the manufacturer is advertising.
You can trust the product if they specify the capacity in continuous wattage or use two separate numbers.
However, avoid products that only specify the peak wattage because there’s no standard way to measure it.
The PSU may supply that wattage for only a few seconds while providing significantly lower power at other times.
For example, a cheap 700-watt PSU may only give you around 250 watts at normal capacity.
Power supplies aren’t 100 percent efficient, meaning they can’t convert all the electricity they draw from the outlet.
Therefore, when buying a PSU, you should aim for at least 80 percent efficiency.
That means the PSU can convert 80 percent of its energy from the outlet.
The remaining 20 percent is wasted in the form of heat.
That’s why your power supply needs a fan.
Reputable power supply brands use the 80 Plus efficiency certification in six variations.
The Gold and Platinum layers offer around 90 percent efficiency, while the Silver rating is around 85 percent.
All of these are great options for home users.
The Titanium and Platinum tiers offer above 90 percent efficiency.
However, the price-to-value ratio of these PSUs isn’t justifiable for home users.
For example, an 80-percent efficient PSU with 700 watts capacity will draw around 875 watts from the wall.
The same PSU draws around 780 watts if it’s 90 percent efficient.
The more efficient a PSU, the less heat it’ll generate, which means less fan noise.
Power supplies with higher efficiency ratings are usually modular and come with higher-quality circuits and cables.
The PSU is the most serious piece of hardware in your PC.
You should only buy your PSU from reputable brands with the appropriate safety certifications.
Otherwise, you risk buying a component that may fail at any moment and potentially kill your other component.
Moreover, companies often don’t cover these situations in their warranties because the customer is at fault for using an unreliable PSU.
You may end up with hundreds of dollars in damages for trying to save a few bucks on a cheap power supply.
Note: In worst-case scenarios, an unreliable power supply could also be a fire hazard since it may lack surge protection.
Frequently Asked Questions
1. Can A Weak Power Supply Damage Your Computer?
Your computer may sustain damage from a weak power supply.
A weak PSU sends a lower voltage to your components, slightly limiting performance.
However, if that voltage is significantly lower than expected, you can experience system instability, display artifacts, lower frame rate, data loss, and in rare cases, hardware damage.
Below a threshold, your components won’t work, but they’re unlikely to sustain permanent damage.
2. Will Upgrading Your PSU Improve System Performance?
Upgrading a PSU will only improve system performance if the previous one is considerably underpowered.
In this case, your CPU and GPU can run at full power, which will likely boost your performance.
However, beyond that, you won’t see any performance gains since the PSU is no longer the bottleneck.
For instance, you can’t expect better performance by switching from a 700-watt unit to a 1000-watt unit if your system only consumes 500 watts.
Doing so will only empty your wallet without any tangible benefits.
3. What Happens If Your Power Supply Is Too Strong?
Installing a high-capacity power supply on a computer won’t cause any damage.
However, it won’t improve performance, either.
Some people claim that a high-power PSU will overcharge your components.
That’s only a myth.
Essentially, once your system receives all the wattage it needs, and there’s enough headroom for less common situations, you won’t see any benefits from increasing your PSU capacity.
It’s enough to buy a product with an 80 Plus efficiency rating from a reliable brand.
Instead of spending money on an overpowered PSU, buy more RAM or an M.2 NVME SSD to boost your system’s performance.