In the process of building a computer， many people believe that “the higher the power supply wattage， the safer it is，” even blindly pursuing kilowatt-level high-power supplies. However， this not only can lead to wasted performance but also increase the burden on the budget. In reality， the core of selecting a power supply is “matching”—choosing a product with appropriate wattage based on the actual needs of the hardware platform， while also considering key indicators such as conversion efficiency and stability. This article will delve into the nuances of power supply selection to help you avoid misconceptions and choose the right one for your needs.
Dispelling the Myth: Higher Power Supply Wattage Isn’t Always Better
Many users believe that “higher wattage means stronger power supply performance and more stable computer operation.” This notion is actually flawed. The primary function of a power supply is to convert mains electricity into the DC power required by computer hardware. Its performance is determined by conversion efficiency， output stability， and other factors， not solely by its wattage. Blindly choosing a high-wattage power supply can lead to a series of issues.
Firstly， there is efficiency waste. The conversion efficiency of a power supply is not fixed; it follows a “U-shaped” curve relative to the load rate. Efficiency is highest when the load rate is between 40% and 60%. When the load rate is too low (e.g.， below 20%) or too high (e.g.， above 80%)， the efficiency significantly drops. If a computer’s actual power consumption is only 400W but it’s paired with a 1000W power supply， the load rate during daily use will often be below 50%. Not only is the conversion efficiency low and electricity wasted， but prolonged operation at low loads can also affect the power supply’s lifespan.
Secondly， there is increased cost. Power supplies with higher wattage typically come with a higher price tag. For mainstream brands， a 500W power supply might cost between 200-300 yuan， while a 1000W power supply could cost over 600 yuan. For typical office， home theater， or mid-range gaming platforms， the premium for a high-wattage power supply is entirely unnecessary. Saving this money to upgrade core hardware like the graphics card or memory can lead to a more noticeable improvement in computer performance.
Finally， there is insufficient practicality. High-wattage power supplies are often larger in size， which might cause installation compatibility issues in smaller cases. Additionally， the number and length of cables for high-wattage power supplies are usually designed for high-end multi-core platforms. When used with ordinary platforms， there will be excess cables， increasing the difficulty of cable management and potentially affecting internal case airflow.
Of course， this does not mean high-wattage power supplies are entirely without merit. For high-end enthusiast platforms equipped with top-tier CPUs， dual graphics cards in SLI/CrossFire， or multi-drive arrays， or for users with clear upgrade plans (such as intending to switch to a higher-power graphics card in the future)， opting for a sufficiently powerful power supply is reasonable. However， for the vast majority of ordinary users， “enough with some headroom” is a more rational choice.
Precise calculation: How to determine the power supply wattage your platform needs
The first step to choosing the right power supply is accurately estimating the total power consumption of your computer platform. The power consumption of computer hardware varies greatly. CPUs and graphics cards are the biggest power consumers， with their combined wattage often accounting for over 70% of the total platform power. Other components (motherboard， memory， hard drives， etc.) consume relatively less. When calculating， focus on the core hardware while also considering the details.
The power consumption parameters for CPUs and graphics cards are usually labeled as “TDP” (Thermal Design Power). However， it’s important to note that TDP is not the actual power consumption. TDP represents the thermal requirement of the hardware under full load， and the actual power consumption during operation may be higher or lower than the TDP. For example， an Intel Core i5-13400F has a TDP of 65W， but its actual power consumption under full load can reach around 100W. An AMD Ryzen 5 7600X has a TDP of 105W， but its full load consumption might even exceed 140W.
When calculating， it is recommended to use the hardware’s “actual full load power consumption” as a reference， rather than TDP. There are two ways to obtain actual power consumption: first， check the official specifications from the hardware manufacturer (some brands will indicate “typical power consumption” or “maximum power consumption”); second， refer to the actual test data from professional review organizations.
The power consumption differences for graphics cards are even more pronounced. Entry-level graphics cards (like the GTX 1650) have an actual full load power consumption of about 75W. Mid-range graphics cards (like the RTX 4060) consume around 120W， while high-end graphics cards (like the RTX 4090) can exceed 450W. It is crucial to clarify the graphics card model when purchasing to accurately match the power consumption.
In addition to CPUs and graphics cards， other components such as motherboards， RAM， storage devices， and fans also consume power. Although the power consumption of individual components is not high， their combined total should be factored in.
Motherboard: A typical ATX motherboard consumes about 20-30W. High-end motherboards with multiple PCIe slots and RGB lighting might reach 40-50W.
RAM: A single 8GB DDR4 memory stick consumes about 3-5W. DDR5 memory consumes slightly more， around 5-7W. For four memory sticks， the total power consumption needs to be doubled.
Storage: Hard Disk Drives (HDDs) consume about 5-10W， while Solid State Drives (SSDs) consume less. SATA SSDs consume about 2-3W， and NVMe SSDs consume about 5-8W.
Other Devices: CPU cooler fans and case fans each consume about 1-2W. RGB lighting and water cooling pump modules might consume about 5-15W.
After calculating the total platform power consumption， you cannot simply choose a power supply with a wattage equal to the total consumption. When a power supply operates at 100% load for an extended period， it generates significant heat， has lower conversion efficiency， and can accelerate aging or even cause failures. Therefore， it is necessary to reserve a certain power margin， typically recommended to be 10%-20%.
For example， if a platform’s CPU has an actual consumption of 100W， the graphics card 120W， the motherboard 30W， RAM 10W， storage 10W， and other devices 10W， the total consumption is approximately 280W. After reserving a 20% margin， the required power supply wattage would be 280W * 1.2 = 336W. In this case， a 400W power supply would suffice. If you plan to upgrade the graphics card in the future (e.g.， to an RTX 4060 Ti with 180W consumption)， the total consumption will increase to 340W. With a 20% reserve， this would require 408W， making a 500W power supply a more robust choice.
For novice users， online power calculators (such as those available on the official websites of brands like Huntkey and Great Wall) can also assist in estimations. After entering the hardware models， the tool will automatically generate recommended power supply wattages， which are simple to use and highly accurate.
Comprehensive Consideration: Beyond Wattage， These Indicators Greatly Affect Your Experience
Once you’ve determined the appropriate wattage， the power supply selection process is not yet complete. Indicators such as conversion efficiency， modularity， power supply architecture， and brand quality directly impact the power supply’s stability， energy saving， and lifespan， and are “hidden elements” that must be carefully considered during selection.
Conversion Efficiency: 80 PLUS Certification is an Important Reference
Conversion efficiency refers to the ratio of AC mains power converted into DC power by the power supply. The higher the efficiency， the less electricity is wasted， and the lower the heat generation. Currently， the industry commonly uses “80 PLUS certification” as a standard for evaluating conversion efficiency. The certification levels， from lowest to highest， are White， Bronze， Silver， Gold， Platinum， and Titanium， with higher levels requiring stricter conversion efficiency. For instance， an 80 PLUS White certification requires a power supply to have at least 80% conversion efficiency at 50% load， and at least 80% at 20% and 100% loads. In contrast， an 80 PLUS Gold certification requires at least 90% efficiency at 50% load， 88% at 20% load， and 87% at 100% load.
For ordinary users， power supplies with 80 PLUS Bronze or Gold certification offer the best cost-performance. Bronze certified power supplies meet basic energy-saving requirements and are affordably priced. Gold certified power supplies have higher conversion efficiency， leading to significant electricity savings over the long term， making them suitable for power-conscious users. It’s important to note that 80 PLUS certification is “voluntary.” Some smaller brands may claim “near Gold efficiency” without obtaining certification， and the actual performance of such products is often questionable. Therefore， it’s essential to look for legitimate certification markings when purchasing.
Modularity Type: Affects Cable Management and Compatibility
Power supplies can be categorized into three types based on their modularity: non-modular， semi-modular， and fully modular. Each type significantly impacts internal case cable management and hardware compatibility.
- Non-Modular Power Supplies: All cables are permanently attached to the power supply unit and cannot be detached. Their advantages include lower prices and high reliability. However， excess cables cannot be removed， leading to clutter within the case and affecting cooling and aesthetics. They are suitable for users with limited budgets and a preference for simple builds.
- Semi-Modular Power Supplies: Core cables (such as the 24-pin motherboard power cable and CPU power cable) are fixed， while other cables (such as graphics card power cables and drive power cables) can be freely detached. They offer a balance between cost-effectiveness and ease of cable management， making them a mainstream choice currently.
- Fully Modular Power Supplies: All cables can be freely detached， allowing users to select only the necessary cables based on their hardware requirements. This offers greater flexibility in cable management， making them ideal for users who prioritize a tidy case interior， though they are generally more expensive.
Power Supply Architecture and Stability: Details Determine Quality
The internal architecture of a power supply directly affects its output stability and lifespan. Current mainstream architectures include ATX 3.0 and ATX 2.52. ATX 3.0 is the latest standard， supporting the 12VHPWR connector for PCIe 5.0 graphics cards and capable of handling higher transient power (up to twice the rated wattage)， offering better compatibility and stability. It is suitable for pairing with new graphics cards like the RTX 40 series and RX 7000 series. If you are using older graphics cards， a power supply with an ATX 2.52 architecture will also suffice， but ensure it is equipped with sufficient 6+2 pin graphics card power connectors.
Additionally， the power supply’s “PFC (Power Factor Correction)” circuit is also important. Active PFC has a higher power factor than passive PFC (closer to 1)， resulting in better energy savings and more stable voltage output. Currently， mainstream power supplies employ active PFC designs， so it’s important to confirm this feature when purchasing.
Brand and Warranty: Avoiding the “Shanzhai Power Supply” Trap
The quality of a power supply directly relates to the safety of the entire computer system. Inferior power supplies may exhibit issues such as bulging capacitors or unstable output voltages， and can even lead to short circuits or damage to other hardware. Therefore， it is crucial to choose reputable brands when purchasing， such as Huntkey， Great Wall， Corsair， Antec， and Super Flower. Products from these brands undergo rigorous testing， ensuring better quality assurance. Furthermore， the warranty period is an important indicator of a power supply’s quality. High-quality power supplies typically have warranties of 5-10 years， with some high-end models even offering lifetime warranties. In contrast， “shanzhai” (knock-off) power supplies often have warranties of only 1-2 years， and after-sales support can be unreliable. Prioritizing products with longer warranty periods can indirectly reflect the manufacturer’s confidence in their product quality.
Other Details: Case Compatibility and User Experience
In addition to core indicators， details such as the power supply’s dimensions， cable length， and fan noise should also be considered. For example， small ITX cases require SFX or SFX-L specification power supplies， while standard ATX cases are compatible with ATX power supplies. The cable length should be sufficient to reach the connectors of your hardware， especially in larger cases， ensuring the CPU power cable and graphics card power cable can easily reach their ports. Regarding fans， power supplies with intelligent temperature control can automatically adjust fan speed based on the load. At low loads， the fan can stop spinning， effectively reducing noise and enhancing the user experience.
The selection of a computer power supply is not about “higher wattage is better，” but rather about “matching the platform’s needs” as the core principle， combined with a comprehensive assessment of factors such as actual power consumption， conversion efficiency， modularity， and brand quality.
For ordinary users， a 400-600W 80 PLUS Bronze/Gold semi-modular power supply is usually sufficient. For mid-to-high-end gaming platforms， a 600-800W power supply can be chosen based on CPU and graphics card power consumption， with a preference for ATX 3.0 architecture. For enthusiast platforms or users with upgrade plans， an 800W or higher fully modular power supply would be more suitable.
