If the CPU is the brain of your computer, then the PSU (power supply unit) is the heart. It’s one of those unsung heroes, quietly doing its job but holding everything together. Without it, nothing works. A good PSU makes sure that your system gets the power it needs to run smoothly, even when the going gets tough. But as computers get more advanced (and power-hungry), the demands on the PSU increase too. It needs to be able to withstand everything from small load spikes to power outages without breaking a sweat.
Unless you’re an expert, please don’t try your own testing at home. We take this stuff seriously (but not too seriously, we promise). Power supplies can be dangerous! We’ll handle the tricky bits.
If you’ve been following along with our other PSU content or already have a good grasp of power supplies, feel free to scroll down to the juicy stuff - our Test List section. Otherwise, stick around for a breakdown of our approach, where we’ll walk you through everything you need to know about how we test power supplies.
Our PSU reviews dive into four key areas:
Hardware: What’s in the box, the construction of the PSU, and the specs.
Features & Software: Modes, warranties, and protection mechanisms.
Performance: Tests like Output Voltage Ripple Sweep and Load Regulation.
Productivity & Efficiency: We check how efficient the PSU is at delivering power without wasting energy.
Each PSU review also gets a video on our PSUCircuit channel for those who prefer a more visual approach. And for the graph lovers, we’ve already covered how to interpret our PSU graphs in a previous post.

Test Setup and Equipment
We’ve designed our test bench to simulate a range of conditions. Here’s a peek at some of the tools that we use:
1. AC Source (Chroma 61507): A programmable AC (alternating current) power source that can give up to 350 volts and lets you fully control how the electricity behaves. It simulates the power from your wall socket.
2. DC Source (Chroma 62012P-80-60): Generates exact DC (direct current) voltages, handy for testing over-voltage protection.
3. ON/OFF Controller (Chroma 80613): It precisely controls when power is connected or disconnected, helping us measure the PSU’s response.
4. SC/OVP Tester (Chroma 80612): This is used for Short Circuit and Over Voltage Protection testing. It works by using internal relays and connecting to a DC source.
5. Timing/Noise Analyzer (Chroma 80611): Measures electrical noise and timing. Think of it as a mix between a high-end multimeter and an oscilloscope.
6. Single Channel Loads (Chroma 63640-80-80) and Dual Channel Loads (Chroma 63610-80-20): Single Channel Loads can handle up to 80 volts or 80 amps, with a maximum of 400 watts. Dual Channel Loads handle up to 80 volts or 20 amps per channel, with a 100-watt limit per channel. Both are used to simulate the load of a computer.
7. Digital Multimeter (Chroma 12061) and Power Meter (Chroma 66205): This digital multimeter gives more accurate readings than a regular one. A power meter can measure the voltage being supplied by an AC source.
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We also use some other tools to gather data with precision such as:
8. Oscilloscope (Rhode and Schwarz MXO58): It is used for taking noise measurements, measuring timing, and capturing waveforms.
9. Environmental Chamber (AES SCH-512-4): A sealed chamber where we can control temperature and humidity, making sure each PSU is tested under consistent conditions.
While it sounds like a high-tech playground, the aim is simple: test PSUs under a variety of conditions and see how they perform.
Now that you know what tools we’re working with, let’s dive into the actual tests.
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The Test List
The purpose of these tests is to put the PSU through its paces, simulating a range of conditions and scenarios it might face in the real world. For those keeping track, our method is based on the ATX guide version 3.1 (as of November 2023). This standard sets out the safety and performance benchmarks we use to judge PSUs. Ready? Let’s power this up.
Output Voltage Ripple Sweep
A PSU in a computer converts the power coming from the wall into power that the computer components are designed to run on. If you try to use high voltage power, the components wouldn’t like that very much. When converting AC to DC, the output isn't perfectly smooth—there are small fluctuations known as ripple or noise. Instead of just a constant DC voltage, the output also has random and repeating changes, called voltage noise or voltage ripple. High-quality PSUs minimize this, resulting in more stable performance.
Our ripple tests are conducted at different input voltages and across various load levels to simulate real-world conditions. We adhere to ATX guides by adding extra capacitors and using a 20MHz bandwidth filter on our oscilloscope for accuracy.
Load Regulation Sweep
For a PSU to deliver stable power, it needs to keep consistent output voltage even as the load changes. Load regulation measures how well the PSU does this. We gradually increase the load in 10% increments, monitoring voltage stability.
One challenge we face in our tests is voltage drop due to the long cables connecting the PSU to the testing equipment. To fix this, we use remote voltage sensing (Vsense), which compensates for any drops by ensuring accurate measurements.
Power Excursion
In the real world, computer components don’t draw a static amount of power—they spike and dip depending on usage. Power excursions test how well a PSU can handle these fluctuations, especially when the load exceeds the unit’s rated capacity. For modern systems, especially with high-end GPUs, the ability to briefly exceed power ratings is important. Our test pushes PSUs up to 200% of their rated load for short bursts to see how they cope.
Even power supplies designed to older ATX versions (pre-3.0) are tested to ensure they can handle modern power demands, despite not being designed with these power excursions in mind.
Power Efficiency Sweep
With rising power demands, efficiency matters more than ever. A PSU that runs efficiently saves energy, reduces heat output, and can even lower electricity bills over time. Most PSUs come with efficiency ratings like CLEAResult 80PLUS or Cybenetics ETA, which show their performance under specific conditions.
We test each PSU at various load points (2%, 10%, 20%, and so on) and temperatures (0°C, 20°C, and 40°C) with both 115V and 230V inputs. These results are compared against the manufacturer’s claims and certifications, giving a complete view of how well the PSU operates across its full load range.
Brownout/Hold-Up Duration
Ever had a momentary power outage that made your computer shut off? Depending on the length of the power cut (brownout), your PSU may be able to weather the storm and keep your computer running. Our brownout tests measure how long a PSU can continue delivering stable power during a temporary loss of input voltage.
We mimic these conditions at 80% and 100% load with both 115V and 230V inputs. The result is graphed using the Power Good (PWR_OK) signal, which shows how long the PSU can stay within safe operating limits during a power interruption.
Over Current Protection (OCP)
OCP is one of the most critical protections in a PSU, preventing circuits from being damaged by excessive current. OCP not only protects the PSU, but is crucial to protecting the user from shock, temperature, or fire hazards. Our OCP test finds the maximum current each output rail (usually the 3.3V, 5V, 5Vsb, -12V, and +12V rails) can handle before OCP kicks in and cuts off power.
We incrementally increase the load on each rail until the OCP triggers. There’s no set standard for where OCP must activate, though it’s essential that it protects both the PSU and the user from damage. And while it's a bit disappointing, it's not a failure if the PSU dies after an OCP as long as it doesn't create a hazard.
Upcoming Tests
We’re also developing a range of new tests that will be rolled out once fully refined. Here’s a sneak peek at what’s in the works:
Audio
Power supplies generate noise from both fans and electrical components. The volume of audio noise can get irritating with load increases or changes. While it’s just one part of the overall noise in a system, a quiet PSU can improve the user experience.
Short Circuit Protection (SCP) & Over Power Protection (OPP)
These protections ensure that a PSU can handle both short circuits and excessive power draw without damaging the system. We’re refining tests for SCP and OPP to ensure your PSU has all the right safety features.
Limitations and Challenges
No testing method is perfect, and there are a few challenges we face:
Endurance Testing: We don’t have the resources to run long-term endurance tests on every PSU. While modern PSUs are designed to last years, actually testing them for that long would be… impractical.
Unit-to-Unit Variance: We only test one sample per model, so we can’t guarantee that every unit will perform exactly the same. If we encounter odd results, we’ll test a second unit, for now we will focus on single-sample testing.
Fully Amped ⚡
If you’ve made it this far, congrats! Now you’re a PSU nerd just like us. Testing PSUs is serious business, but it’s also a lot of fun (for us, at least!). We hope this peek behind the curtain gives you a better understanding of what goes into making sure your PSU is up to snuff.
Remember, PSUs are more dangerous than they look! Leave the heavy lifting to us, and stay tuned for more PSU test results and reviews on our PSUCircuit channel.
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Bibliography
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