Does PC Power Supply Use Constant Wattage?

The power supply unit is a critical component of a computer, but it is rarely discussed. Without it, the computer is unusable. For most of us, once we’ve turned on the computer, what we’re immediately looking at is the computer’s performance, unmindful of the humble power supply that’s primarily breathing life to the computer. Let’s get into the details of what a power supply is, its importance to the computer’s ecosystem, and how it supplies wattage to the computer.

What is a Power Supply Unit?

A power supply unit (PSU) is a vital component of the computer that sources power from the primary source (the power coming from your wall outlet) and delivers that power to its motherboard and all its components. Contrary to the common understanding, the PSU does not supply power to the computer; it instead converts the AC (Alternating Current) power from the source to the DC (Direct Current) power that the computer needs.

There are two types of PSU: Linear and Switch-mode. Linear power supplies have a built-in transformer that steps down the voltage from the main to a usable one for the individual parts of the computer. The transformer makes the Linear PSU bulky, heavy, and expensive. Modern computers have switched to the switch-mode power supply, using switches instead of a transformer for voltage regulation. They’re also more practical and economical to use because they’re smaller, lighter, and cheaper than linear power supplies.

Watt’s in a Watt?

The unit of power is Watt. We usually see how many Watts a power supply can provide on its label. Most PC already has a built-in power supply, so it’s a minor concern when buying a new computer. However, if you have upgraded or have added new components to your computers, like a new hard drive or a new cooling system, then it’s time to check the amount of power your computer’s PSU can deliver. If the total power the computer needs is more than what the power supply can deliver, it simply won’t work. The question now is, “How many watts does my computer need?” That would depend on the total amount of power the computer needs, based on the power each component requires. Simple computers don’t really require that much power, but complex systems, like those used for gaming, would generally require higher-wattage PSUs since they have higher-end components and have a lot more components than the average, day-to-day computer.

Another puzzling question for most consumers is, “Does a PSU supply constant wattage to the computer?” The answer is a flat No. The wattage you see on the PSUs casing or labels only indicates the maximum power it can supply to the system, theoretically. For example, by theory, a 500W PSU can supply a maximum of 500W to the computer. In reality, the PSU will draw a small portion of the power for itself and distributes power to each of the PC components according to its need. The amount of power the components need varies from 3.3V to 12V. If the total power of the components needs to add up to 250W, it would only use 250W of the 500W, giving you an overhead for additional components or future upgrades.

Additionally, the amount of power the PSU supplies varies during peak periods and idle times. When the components are pushed to their limits, say when a video editor maximizes the GPU for graphics-intensive tasks, it would require more power than when the computer is used for simple tasks like web-browsing. The amount of power drawn from the PSU would depend on two things; the amount of power each component requires and the tasks that each component performs.

Power Supply Efficiency

Another source of confusion concerning PSUs is their efficiency rating. When PSU converts the AC power to DC, some of the power is wasted and is converted to heat. The more heat a PSU generates, the less efficient it is. Inefficient PSUs will likely damage the computer’s components or shorten their lifespans in the long run. They also draw more power from the primary source resulting in higher electricity bills for consumers.

You might’ve seen 80 PLUS stickers on PSUs or its other variants like 80 PLUS Bronze, Silver, Gold, Platinum, and Titanium. 80 PLUS is the power supply’s efficiency rating; the power supply must reach 80% efficiency to be certified. It’s a voluntary standard, which means companies don’t need to abide by the standard, but 80 PLUS certifications have become popular because a more efficient power supply can lessen the consumers’ carbon footprint and help them save some bucks on their electric bills. Below is the efficiency rating that a PSU needs to achieve to get the desired rating.

Certification Levels Efficiency at 10% Load Efficiency at 20% Load Efficiency at 50% Load Efficiency at 100% Load
80 PLUS 80% 80% 80%
80 PLUS Bronze 82% 85% 82%
80 PLUS Silver 85% 88% 85%
80 PLUS Gold 87% 90% 87%
80 PLUS Platinum 90% 92% 89%
80 PLUS Titanium 90% 92% 94% 90%

It’s important to note that the 80% efficiency does not mean that the PSU will only supply 80% of its capacity to the computer. It means it will draw additional power from the primary source to only 20% of power is lost or generated as heat during the conversion. A 500W PSU will therefore draw 625W of power from the main to make it 80% efficient.

The Power of Power Supplies

Like in most electrical appliances, power supplies play a vital role in the computer’s functionality. There are two critical things to consider when choosing a PSU – capacity and efficiency. PSUs do not deliver a constant amount of power to their components since this would depend on the task that each component of the computer performs. Always make sure that you choose a PSU with more wattage than the total power that your computer needs to make sure that the components would get the power that they require to prevent malfunction. This will also provide leeway for additional components and future upgrades. Aside from capacity, it’s also worth noting the PSU’s efficiency rating. An efficient PSU will lower your electric bills and help the environment by reducing your carbon footprint.

Choosing Best Uninterruptable Power Supply (UPS)

When power shuts down all of a sudden, servers become unresponsive or, even worse, corrupted. Under these circumstances, owning the best UPS for home and office becomes a necessity.

Attributes to consider when picking the Best Uninterruptible Power Supply include:

  • battery lifetime
  • cost
  • noise levels
  • ports
  • manufacturer’s warranty
  • style and design
  • setup process
  • control display
  • size of device
  • comes with software?

About the author

Glynis Navarrete

A freelance blogger who loves to write about anything related to technology. Born and raised in the Philippines and worked in Singapore for eight years as Technical Support for a wide range of IT equipment. Took a dive into the world of freelancing and now enjoying doing what I’m passionate about while not losing touch with technology.