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The PFC of a power supply unit is a technology that improves power efficiency and reduces waste.
By supporting PFC, the power supply can deliver electricity more efficiently, leading to benefits such as saving on electricity bills and improving stability.
In recent power supply units, about 80% support PFC. However, there are different types of PFC, and knowing how to read the specifications makes it easier to choose the right one. This article will explain these points as well.
- PFC is a technology that improves the power efficiency of power supply units
- It increases power factor, helping to save electricity costs and improve stable operation
- There are two types of PFC: Active PFC and Passive PFC
- Active PFC improves power factor to 0.9 or higher and is highly energy efficient
- Passive PFC is low cost but its improvement effect is limited (currently rarely used)
- About 80% of recent power supply units adopt PFC
- There is little price difference between supported and unsupported models
- Check the product specifications for the type of PFC and specific power factor
This article also explains the basics of power supply unit standards, cables, and how to choose from the perspectives of performance and compatibility.
≫ Related article: How to Choose a Power Supply Unit for a Custom PC [Performance / Features / Compatibility]
Select PC parts and online stores to instantly generate an estimate, check compatibility, and calculate power requirements. You can save up to five different builds, making it easy to try out multiple configurations.
≫ Tool：PC Parts Estimation & Compatibility Check Tool
Table of Contents
About PFC in Power Supply Units
This section explains the basics of PFC in power supply units.
What is PFC in Power Supply Units?
PFC (Power Factor Correction) is a technology that improves the power efficiency of power supply units and reduces unnecessary power consumption.
A power supply unit converts AC power to DC power, but some power is wasted during this conversion process.
PFC minimizes this waste by allowing the power supply unit to use electricity more efficiently.
Specifically, PFC reduces unnecessary power consumption by matching the phase (timing) of current and voltage when the power supply unit consumes electricity.
This allows more efficient use of electricity supplied by the power company, leading to savings on electricity bills and reducing environmental impact.
About Power Factor
Power factor is an indicator of how efficiently electricity is being used.
Specifically, it shows the proportion of supplied power that can actually be used by devices.
Power factor is calculated as follows:
Active Power (W / Watt): The power that devices can actually use
Apparent Power (VA / Volt-Ampere): The total power supplied from the power source
Power Factor = Active Power (W) ÷ Apparent Power (VA)
The value of power factor ranges from 0 to 1. The closer it is to 1, the more efficiently electricity is being used.
For example, if the power factor is 1.0 (100%), all supplied power is used without waste. If the power factor is 0.6 (60%), 40% of the supplied power is wasted.
In power supply units and home appliances, the timing (phase) of current and voltage can shift due to coils and capacitors, which can lower the power factor.
This wasted power is called “reactive power” and is a burden for power companies. It can also cause higher electricity bills at home.
By using a power supply unit with PFC, the power factor can be improved, reducing wasted power and improving power efficiency.
The power factor of a typical power supply unit is about 0.6 to 0.7, but with active PFC, the power factor can be as high as 0.9 to 0.99, which provides significant energy-saving effects.
About 80% of Power Supply Units Use PFC
In recent power supply units, about 80% of products use PFC.
In most cases, PFC is supported, so narrowing down the selection to only PFC-supported power supplies will not drastically reduce the number of options.
Therefore, it is relatively easy to choose a PFC-supported power supply.
The 80% figure is based on data from the Custom PC Parts Estimate & Compatibility Check Tool.
This tool allows users to search for power supply units that support PFC, so it is recommended to use it.
However, as will be explained later, the tool does not support searching by PFC type or detailed specifications, so to check the specific power factor, it is necessary to refer to the specification page of each product.
Types of PFC
This section explains the types of PFC and the approximate power factor for each.
Active PFC
Active PFC is a PFC that uses electronic circuits to adjust the waveform of the current.
This reduces power waste and allows the power supply unit to do the same work with less electricity.
The advantages of active PFC are as follows:
- Improved power efficiency
By bringing the power factor close to 1, electricity supplied by the power company can be used more efficiently. - Electricity cost savings
Lower electricity bills due to reduced power loss.
- Improved stability
Provides stable output even when input voltage fluctuates, ensuring stable operation of devices. - Reduced environmental impact
Improves the efficiency of the entire power supply system, reducing environmental burden.
On the other hand, the disadvantages of active PFC are as follows:
- Increased manufacturing cost
Adding an active PFC circuit increases the manufacturing cost of the power supply unit. - More complex circuit design
Compared to passive PFC, the circuit is more complex, making design and manufacturing more difficult.
The most concerning point is whether the price increases with active PFC support, but honestly, there is not much difference.
It is difficult to find power supply units with exactly the same specifications except for PFC support, so the pure price difference between supported and unsupported models is unclear.
However, after checking the prices of power supply units by support status, there does not seem to be much difference.
Rather, the price is more affected by power capacity, 80 PLUS certification, and other features.
Passive PFC
Passive PFC is a PFC that uses large coils (inductors) and capacitors to adjust the current waveform and improve power factor.
This reduces power waste and allows more efficient use of electricity supplied by the power company.
The advantages of passive PFC are as follows:
- Low cost
Simple structure and low cost. - High reliability
Fewer parts mean less chance of failure, so reliability is high.
On the other hand, the disadvantages of passive PFC are as follows:
- Limited power factor improvement
Power factor is usually about 0.7 to 0.8, so the improvement is limited.
However, in the current custom PC power supply market, active PFC is more efficient and meets the standards for 80 PLUS certification more easily, so passive PFC is rarely used.
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Especially for 80 PLUS certified power supplies, active PFC is almost always included.
If a power supply with passive PFC is found, it is likely an old or low-quality product, so it is best to avoid it.
Table of Power Factor by Type
Here is a summary of the approximate power factor and features for active PFC, passive PFC, and no PFC.
| Type of PFC | Approximate Power Factor | Advantages | Disadvantages |
|---|---|---|---|
| Active PFC | 0.9–0.99 | ・High power factor and good power efficiency ・Saves on electricity bills ・Improved stability ・Reduced environmental impact | ・Higher cost ・Complex circuit |
| Passive PFC | 0.7–0.8 | ・Low cost ・Simple structure | ・Limited improvement effect |
| None | 0.6–0.7 | ・Low cost | ・Poor power efficiency ・Generates more heat |
How to Check PFC Support
This section explains how to check if a power supply unit supports PFC, what type of PFC it uses, and its efficiency.
Check the Product Specifications of the Power Supply Unit
To check if a power supply unit supports PFC, what type of PFC it uses, and its efficiency, look at the product specifications.
It says “Active PFC (PF>0.9 at full load)”, which means the unit supports active PFC and the power factor is 0.9 or higher even at maximum load.
Some products may only say “Active PFC” without specific numbers like 0.9.
There are many websites where PC parts can be searched, and many allow searching for power supply units by PFC support. However, it is rare to be able to search by PFC type or specific power factor, so for detailed specifications, refer to the official page of each product.
Search with Custom PC Tools
With the Custom PC Parts Estimate & Compatibility Check Tool, it is possible to narrow down the search to power supply units that support PFC.
Also, each power supply unit has a link to its product page, so if detailed specifications are needed, it is convenient to access them directly without searching by product name.
Summary: PFC-Supported Power Supply Units are Recommended for Saving Electricity and Stable Operation!
This article explained the basics of PFC in power supply units, recent support status, and how to check specifications in detail.
Here is a summary of the key points.
- PFC is a technology that improves the power efficiency of power supply units
- It increases power factor, helping to save electricity costs and improve stable operation
- There are two types of PFC: Active PFC and Passive PFC
- Active PFC improves power factor to 0.9 or higher and is highly energy efficient
- Passive PFC is low cost but its improvement effect is limited (currently rarely used)
- About 80% of recent power supply units adopt PFC
- There is little price difference between supported and unsupported models
- Check the product specifications for the type of PFC and specific power factor
PFC is an important technology for improving power efficiency, saving on electricity bills, and increasing stability. Basically, it is recommended to choose a power supply unit that supports active PFC.
This is especially recommended for those who use custom PCs for long hours or need stability for high-load applications.
Since about 80% of power supply units support PFC, choosing a PFC-supported product does not significantly reduce the options for power capacity or other features, making it easy to select.
This article also explains the basics of power supply unit standards, cables, and how to choose from the perspectives of performance and compatibility.
≫ Related article: How to Choose a Power Supply Unit for a Custom PC [Performance / Features / Compatibility]
Select PC parts and online stores to instantly generate an estimate, check compatibility, and calculate power requirements. You can save up to five different builds, making it easy to try out multiple configurations.
≫ Tool：PC Parts Estimation & Compatibility Check Tool
