Supplemental PC Power Supplies

You may need an extra power supply for your video card

Gaming PCs that are capable of running several graphics cards often require more wattage than your computer's power supply can handle. A supplemental power supply can give your graphics card the external power it needs to render high-resolution video.

Photo of a Corsair Enthusiast TX650 V2 ATX12V EPS12V Power Supply
Corsair Enthusiast TX650 V2 ATX12V EPS12V Power Supply. © Corsair

What Is a Supplemental Power Supply?

A secondary power supply resides within a desktop computer case, adding additional power capacity to the entire system. They are typically designed to fit into a 5.25-inch drive bay. The incoming power cable is routed through an available card slot on the back of the system. Various component cables run from the supplemental power supply to your internal PC components.

Because the most common use for these devices is to power the latest generation of energy-hungry graphics cards, they almost always have PCI-Express graphics 6-pin or 8-pin power connectors. Some also feature 4-pin Molex and Serial ATA power connectors for internal drives.

Due to the limited size of supplemental power supplies, they tend to be a bit more restricted in their overall maximum power output compared to a standard power supply. Typically, they are rated around 250 to 350 watts of output.

While it's possible to replace an existing power supply in a system with a newer, higher-wattage unit, installing a supplemental power supply is generally easier than replacing the primary unit.

Why Use a Supplemental Power Supply?

In addition to sufficient RAM, you need an adequate power supply for your computer's graphics card to properly render moving 3D images. When a graphics card is installed into a system that either lacks the proper wattage output or lacks the proper power connectors, a secondary power supply is necessary.

They can also be used to provide additional power for internal components, for example, if you're using a large number of hard drives. Some desktop computer systems use proprietary power supply designs, so you can't replace the main power supply; however, you can still add a supplemental supply to boost its capacity. Therefore, supplemental power supplies are an excellent choice for expanding the capabilities of a system without completely rebuilding it.

Reasons Not to Use a Supplemental Power Supply

Power supplies are a major generator of heat within computer systems. The various circuits that convert the wall current down the low-voltage lines inside the system generate heat as a by-product. With a standard power supply, this isn't too much of a problem, as they are designed for airflow into and out of the case.

Since a supplemental power supply resides inside the case, it creates extra heat. For some systems, this won't be a problem if they already have sufficient cooling to handle the extra heat buildup. Other systems will not be able to cope with this extra heat, which could lead to the system shutting down or potential damage to circuits. Before adding a supplemental power supply, examine your system to see if it can handle the heat burdens it would generate.

Avoid installing supplemental power supplies in desktop cases that hide the 5.25-inch drive bays behind a door panel. The door will prevent the sufficient flow of air and will be more likely to overheat the system.