Tips On How To Check Power Supply Wattage Without Opening

Every computer needs electric power to work. It gets power from a power supply unit. However, power requirements vary between devices. What this means is that two computers may not need the exact minimum amount of power to function. 

The power ratings of a computer’s power supply unit inform us of its minimum power requirements in Watts.

The most common method of checking your power supply wattage is to open up the computer and check the power supply ratings on the power supply unit. But do you know you can find out your power supply wattage without opening your device? Read on to learn more!

How You Check Power Supply Wattage Without Opening Your Computer

  1. Check the manufacturer’s website: If you use a prebuilt PC, go to the manufacturer’s website and search for your model’s device specifications. Most manufacturers provide all necessary information about their products on their websites.
  2. Check the power supply box or packaging: You can also check the power supply box or packaging. Most manufacturers indicate the power supply specifications and ratings on the body of the box. 
  3. Check the power supply manual: Some power supplies also come with international manuals. In addition, some manuals contain information on the product’s power supply ratings. 

So, what’s the significance of power supply wattage? What does it mean to you, the end-user? We will first examine the concept of the power supply in more broad terms. So, continue reading to find out more.

What Is Power Supply?

A power supply is the computer component that delivers electric power to all other parts. Manufacturers rate power supply in terms of the Watts they produce. A higher wattage rating indicates that it supplies more power.

A power supply has two main functions. First, it converts an electric current from an external power source into a form usable by your computer and then distributes it to all the components. Second, it regulates the voltage that passes through your computer to avoid overheating.

Before we delve into how a power supply works to carry out these functions, we’ll first examine the parts that make up a power supply unit.

What Is Power Supply Wattage?

Power supply wattage refers to the amount of power a power supply unit can deliver to a system under full load within a particular time. Wattage is the amount of electricity expressed in Watts. Watt is the unit measurement of electric power.

How Much Wattage Does Your PC Need?

The amount of power you need depends on the computer’s build, your day-to-day activities, and your running programs.

Your computer’s graphics cards, processor, and disk drives take the most power. So knowing their specifications will help you determine your computer’s power needs. 

For example, a computer with low to mid-range graphics will require between 165-200W, while high-end graphics will take up no less than 350W. 

So, add that to the primary power requirements of other components, and you can have a grasp of your computer’s wattage requirements. 

Why Should I Care About My Power Supply Wattage?

The power supply gets relatively little attention compared to other components like the graphics card and memory. However, it is arguably the most critical component of a computer system because the system cannot function in the first place without it.

A power supply not only gives power to your device but also contributes to its overall function. For example, it determines how stable and reliable your system will be.

For example, a power supply with high wattage ratings will supply more power to your computer. Other factors that should concern you in terms of power supply ratings are the efficiency and the rail.  We will treat those later. Let us first consider how a power supply unit works.

How A Power Supply Works

We already stated that a power supply converts power into usable form and regulates voltage to prevent overheating. So how does a power supply carry out these functions?

A typical power supply unit functions using four main parts: a transformer, a rectifier, a filter, and a voltage regulator.

A transformer adjusts the incoming voltage to meet your computer’s requirements. In essence, a transformer may either lower or increase the incoming voltage level. 

More often than not, the incoming voltage is usually higher than the required voltage.

 A rectifier converts alternating current into direct current. A rectifier may either be a half-wave, a full-wave, or a bridge. 

For you to understand what these types of rectifiers mean, note that power conversion from alternating current to direct current takes a complete cycle. So, half-wave rectifiers use only one-half of the conversion cycle, while full-wave rectifiers use the complete conversion cycle.

A bridge rectifier is a full-wave rectifier that does not involve the functions of the transformer. Instead, a rectifier uses four diodes in place of a transformer.

The direct current produced from the conversion of alternating current contains some ripples or waves. Therefore, it needs a filter to smoothen these waves. However, although a filter creates a smoother current, it does not eliminate all the ripples.

Finally, voltage regulators complete the finishing. They remove the voltage ripples left by the filters as these could either cause power drops or overheating.

So let’s tie all this information together. First, an alternating current enters a computer through the power supply. Next, the transformer either steps it up or down depending on requirements. Then, the rectifier converts it to direct current and passes it on to the filter. 

The filter reduces the voltage ripples in the current but not entirely. Then, the voltage regulator removes the leftover waves from the filter. So what your system will be getting is a smooth, adequate, steady supply of current. Interesting, isn’t it?

How To Choose A Power Supply

There are so many power supply products in the market that do not meet quality standards. Using a substandard power supply may affect your computer in the long run. 

While there’s so much interest regarding CPUs and GPUs, it’s worth knowing how to choose a suitable power supply. There are some essential factors you need to consider to help you select a proper power supply. 

Before we go over more technical aspects of the guidelines, you must first source your power supply from reputable manufacturers. It’s no use looking for a good quality product from unverified producers.

Every power supply comes with specifications. You should consider three essential specifications before purchasing: output (wattage), efficiency, and rails. 


Manufacturers designate the power output of their power supply in watts. A higher-wattage power supply can deliver more power. Desktop power supply ratings range from 200 to 1800 watts. 

Higher wattage ratings exceed the capacity of a standard 15-AMP electrical outlet. The most important rating is the one that represents sustained power instead of the one that represents peak power. Most power supplies can only function at such peak capacity for a short time.

Your power supply unit should, in theory, provide enough power to your components while also providing some extra headroom, in case you choose to add more later. With loads ranging from 40 to 80 percent, most power supplies achieve their maximum efficiency. 

A PSU’s build should be about 50 to 60 percent of its capacity to achieve optimal efficiency while leaving room for future development.


A power supply’s efficiency rating is a mathematical expression defined as the ratio of output to input power. In simpler terms, efficiency is the amount of electric power the supply unit delivers to other components relative to its power from the power source.

So, if your power supply has an 80% efficiency rating, it will supply at least 80% of its rated power in Watts and lose the remaining 20% as heat.

The popular recommendation is to go for a power supply with efficiency ratings of at least 80% as they offer the best value.


A computer’s power supply transforms AC electricity into a series of DC voltages, each of which we call rail. The term rail comes from the power lines that run through the motherboard. Rails may be single or multi-rail.

A single-rail power supply unit powers the system through a single high-power +12V rail. A multi-rail splits its output between two or more +12V rails. Thus, components attached to the supply unit will receive all the power from the supply in a single-rail design, regardless of the connector used.

A multi-rail power supply, on the other hand, will balance the output across multiple points. There has been a long-term debate about the safety of single or multi-rail power supply. Some experts believe that a multi-rail power supply provides more protection to your system.

According to that school of thought, in the event of a breakdown, a single-rail power supply may offer significantly more current to your components.


A power supply unit transforms alternating current to direct current and distributes it to other computer components. Power supplies have ratings in Watts, which is the power they can supply to the system.

The most common method of checking power supply wattage is opening up the computer casing for your power supply unit and checking the wattage ratings.

However, if you own a prebuilt computer, you can check your power supply’s wattage without opening your computer. Instead, go to the manufacturer’s website and check for your model’s specifications.

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