How Many Volts Does a Computer Use?

How Many Volts Does a Computer Use?

We run into desktop problems almost regularly. Overheating CPUs is a very common problem, and it could be happening because your Power Supply Unit (PSU) is working to its full capacity. So first you need to know how many volts your computer PSU uses.

An average personal computer uses 110 volts. This, however, is completely dependent on the power consumption values of different components of the CPU. So a desktop computer can use anywhere from 100 to 450 watts of power to run efficiently.

Considering the big differences between the volt usage, it can seem hard to decide what sort of power supply one should need. I will do a breakdown of how many watts most common components of computer use, and whether to opt for a higher or lower voltage power supply. And more importantly, we will see how a power supply unit works.

Breakdown Of Voltage Use

Some computers run efficiently with less than 100 volts, while some crash even while using 300 volts. The answer lies in how much energy each of the components in the computer consumes.

When every available slot on the motherboard or every available drive bay in the personal computer case is in use, the computer can easily use over 400 watts.

On average, each functioning component of the personal computer can use the following range of wattage:

ComponentPower Consumption
Accelerated Graphics Port (AGP) card20 to 30W
Peripheral Component Interconnect (PCI) card5W
Small computer system interface (SCSI) card20 to 25W
Network interface card4W
50X CD-ROM drive10 to 25W
RAM10W per 128M
5200 RPM Integrated Drive Electronics (IDE) hard disk drive5 to 11W
7200 RPM IDE hard disk drive5 to 15W
Motherboard (without CPU or RAM)20 to 30W
550 MHz Pentium III30W
733 MHz Pentium III23.5W
300 MHz Celeron18W
600 MHz Athlon45W

A computer, when bought, will come with a power supply unit capable of handling almost twice the power usage by the computer. However, if you are building one, it is important to take note of the energy consumption of each component.

Always remember to get a power supply unit that will not have to work at its full capacity.

Does High Voltage Consumption Cause Overheating?

It is clear that a high-performance computer, like a gaming computer, will require a lot more voltage than an office computer. A higher power consumption easily means a higher temperature. This is definitely a reason why gaming computers require more complex cooling systems.

So, should you always use a computer that consumes low voltage?

The answer depends on the type of work needed. For an author, a computer with a 250-watt power supply is enough, while a gamer may consider a computer with a 600 watt PSU.  The necessity for efficiency thus dictates the amount of voltage your computer should be able to use.

While it is true that a high voltage will cause overheating, a substantial part of it can be avoided by using the right power supply unit. Most power supply units don’t heat up until they reach close to full capacity. So, using a 600 watt PSU in the computer that uses 400 watts will help you avoid any problems related to overheating.

Does Low Voltage Consumption Cause Inefficiency?

Simply thinking, lower voltage consumption will result in lower efficiency. As we can see in the power usage breakdown, a computer will need more voltage use for better performance.

That being said, the definition of better performance depends on the type of work and the budget you have for a computer. So, a computer using 100 volts or less may turn out to work the best for you.

The high energy consumption, when not needed, can become an efficiency problem instead of becoming overheated. You may think of the computer mechanisms the same as an incandescent light bulb. While it requires a lot of voltage, it similarly takes a lot of time to cool down.

If you ever touched a 60W light bulb right after turning off the switch, you will know how much heat it traps. So for a 250W computer, it is very easy to assume that it will heat up almost five times more and also take five times longer to cool down.

So for long-time use with simple cooling systems, a lower voltage will prove to be more efficient.

How Does A Power Supply Unit (PSU) Work?

PSUs work by altering input AC power to output DC power. Alternating current (AC) voltage is the flow of charge which changes direction periodically. Direct current (DC) is the constant voltage or current. AC is produced by the alternator, and it is changed into DC through a rectifier, batteries, or an AC generator that is equipped with a commutator.

The power supply unit takes the normal 220 volt AC supply and converts it into 3.3V, 5V and 12V DC. This complex combination of DC voltage is important for the personal computer to function properly.

3.3 Volts

3.3 Volts are necessary to power the CPU. The components that require this voltage are chipsets, DIMMS, cards like PCI, AGP, PCIe, and various chips. Both +3.3 volts and –3.3 volts are available from the power supply. The 3.3V wires from the PSU are color-coded with orange.

5 Volts

5 Volts are used for the chassis and CPU fan or USB ports. It powers components like disk drive logic, low-voltage motors, SIMMs, PCI/AGP/ISA cards, etc. In color-coded PSU wiring, red denotes +5 volts DC while white denotes –5 volts. In modern computers, the negative volts are almost obsolete.

12 Volts

12 Volts usually feed the mainboard and any new generation graphics cards. It can also be used for some smart chassis fans. +12 volts have yellow wires while –12 volts are denoted by blue wires.

Today, the power supply units that you see are all equipped with several safety circuits that check the flow of current continuously to detect extreme power output conditions. This is why a crashing PSU is much more common than a PSU catching on fire.

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