Does a hard drive need power?

You may have noticed that some hard drives come with a power adapter while others don’t which begs the question do hard drives need power?

Hard drives require power to operate, depending on the type of drive an HDD requires either 5v or 12v. %v can be supplied through USB while hard drives that need 12v typically require a power adapter (external drives) or direct connection to the PSU (power supply unit) for internal drives. 

So while all hard drives need power, depending on your drive you may find you have an issue getting a drive to work properly without the correct connection, in this article we will look at how to identify what power connection you need and how to tell.


hard drive in computer

Why does a hard drive need power?

Both HDDs (Hard Disk Drives) and SSDs (Solid State Drives) require power to operate. This is because they are electronic devices that function as data storage components of computer systems.

HDDs are comprised of several parts and fall under the category of electromechanical devices as they have moving parts. These include the disks where the data is stored, the motor that spins the disks, and the armature and head that reads the disk, it is a similar concept mechanically to a record player, only a lot smaller, faster, and more precise.

The HDD needs power so that the individual components can operate enabling the drive to store data. The data is stored via a magnetic charge on a ferromagnetic film that coats the disks. HDDs don’t require power to continue to store data as the charge remains in its polarized state until the disk is rewritten.

SSDs work slightly differently, they have no moving parts and instead store the data in the form of electrical charges. These charges can represent a 1 or 0 in the same way as magnetic polarization can which is used to store data in binary.

SSDs need power to not only write the charges but also to read them and transmit the data to the computer. The amount of power need to do this is dramatically decreased compared to HDDs making SSDs more efficient to run. They run on a 5v supply or 12 supply which is stepped down internally in the drive to meet the requirements of the individual drive.

What type of power does a hard drive need?

HDDs come in various sizes, most commonly 3.5″ and 2.5″ for desktops and laptops respectively. This is where the power requirements deviate. 3.5″ drives need a 12v power supply to run the larger motor, where 2.5″ drives that have a smaller motor can run on 5v directly.


When a desktop computer is plugged in, the power cord is connected to the PSU (Power Supply Unit). The PSU then delivers power to the individual components.

Hard drives are powered by the PSU directly to the drive itself via a SATA power cable which has both a 12v and 5v connection. The drive is then also connected via a data interface cable to the motherboard. This is usually a SATA cable. In larger drives, the 12v connection is used for the mechanical components and the 5v connection for the circuitry. In smaller drives, the 5v rail is used to power both and the 12v connection is either stepped down or routed back through the ground connection.


When a laptop is plugged in the voltage is regulated in the cable via a transformer that converts the AC power supply to a DC power supply, usually to 12v as standard, from there the process is the same to transmit data to and power the hard drive.


This comes into play when using different drives for external purposes. A 3.5″ drive that runs on 12v will not be able to draw enough power from a 5v USB connection (up to USB 3.0, USB-C can deliver 12v) and will therefore require a power adaptor.

2.5″ drives and SSDs can operate from a 5v USB connection so typically only require a single cable unless the drive is designed to make use of the 12v connection.

What type of cables are needed for an internal hard drive?

Internal hard drives, both HDD and SSD use the SATA interface as standard. SATA (Serial AT Attachment or commonly serial ATA) is a standardized port for connecting mass storage media like HDDs or optical drives to a computer.

It requires two cables, a SATA data cable, and a SATA power cable. Some PSUs have unique connectors and may require a converter so it is worth checking your PSU to see if you require any extra converters.

You may also need a splitter if your PSU doesn’t offer enough power output connectors just be sure to check the power output of your PSU first to ensure adding a drive won’t overload it.

It is highly recommended to buy good quality cables for your drives as bad cables can lead to device failure and reduce speeds of data transfer, they have even been known to completely fry drives. Here are our top recommendations. CHECK YOUR PSU CONNECTORS FIRST.

What type of cables are needed for an external hard drive?

External drives usually drive specific when it comes to the cables that they need. The first step is to check with the manufacturer guidelines as to what type of cable it needs. Most drives will use a USB connection but there are various types of USB connection that have different capabilities. This is why you might find simply plugging a cable in doesn’t work, it could be that the cable isn’t able to transmit both data and power or the even right amount of power.

If you need a replacement power adapter then you will have to find the specs of your drive and order a new one from the manufacturer or that meets the specs.

If you require a replacement cable then it is highly recommended to buy a good quality one. As stated before cheap cables could potentially destroy your drive and make the data unrecoverable.

If you know you need a USB cable and what type you need then here are recommendations for 2.0 mini, 2.0 micro, 3.0 , and type-C.

How to power an internal drive externally.

To power an internal drive externally you simply require an adapter to change the internal connections that arent available outside of your computer case to ones that are. This can be done in two ways.

Either you can buy a case for the drive that has the adapter built-in or you can buy the adapter itself which makes it easier to change the drives while only having to buy one thing. These are available for both 3.5″ drives and 2.5″ drives. The 3.5″ version comes with a power adapter.

Below are my personal recommendations for a 2.5″ adapter, 3.5″ adapter, 3.5″ enclosure, and a 2.5″ enclosure. I have all of these myself and use them regularly.

In conclusion, all drives need some form of power and hopefully, you understand a little bit more about why different drives have different power supplies. It can be frustrating trying to power a 3.5″ drive when you only have the cable for a 2.5″ drive lying around! No matter what power your drive needs remember this one thing above all else, BACK IT UP!!