Your power supply unit, or PSU, feeds every other part of the PC. A poor match can limit what you install, and a wrong cable can damage components. This guide does not rank products. It sets out the criteria that makers and test labs document, and says where each one stops being informative.

Gimaxo has not tested any power supply for this guide, so you will not find model picks or prices. Statements come from named pages, listed at the end. Where a sentence starts with “Our reading:”, it is this guide’s own conclusion, drawn from the source named just before it.

Photo: Project Kei, CC BY-SA 4.0, resized and converted (see Image credits). The sockets of one modular power supply with cables plugged in, shown as an example. It does not show whether those cables suit that unit. Not tested or chosen by Gimaxo.

What an 80 PLUS label tells you

80 PLUS is a certification program for the efficiency of internal power supplies. Efficiency is the share of the power drawn from the wall that reaches the components instead of being lost as heat. CLEAResult, which runs the program, describes the specification as at least 80% efficiency at 10%, 20%, 50% and 100% of rated load, with a true power factor of 0.9 or higher. The program has seven levels, from Standard to Ruby, at increasing efficiency.

The program page describes efficiency and power factor. It does not describe protection circuits, voltage regulation or build quality. Our reading: an 80 PLUS level answers an efficiency question, and the other questions need other documents.

Which connector your graphics card uses

Start from the graphics card, not the power supply. NVIDIA’s comparison page for GeForce cards lists, for each model, a Total Graphics Power, a Required System Power and the required power connectors. For many models it lists either several 8-pin PCIe cables, with an adapter in the box, or a single PCIe Gen 5 cable of a stated wattage. Check that your supply provides what your card’s row lists.

Two connector names come up. According to Corsair, the 12VHPWR connector, with 12+4 pins, made its debut with the GeForce RTX 40 series, with a promise of up to 600 W through one cable. Corsair describes its revision, 12V-2x6, as not a new cable but an updated change to the pins in the socket: shorter sensing pins (1.5 mm) and conductor terminals 0.25 mm longer. It says existing 12VHPWR cables and adapters work with the new connector, and presents the change as aimed at reliability. Gimaxo did not read the connector specification itself, so these are Corsair’s statements.

Seating matters with either one. In November 2022, NVIDIA said it was aware of about 50 cases globally involving the GeForce RTX 4090 power connector. It said a common issue was connectors not fully plugged into the graphics card, and advised plugging the power cable into the card first, firmly and evenly. Our reading: the revised connector does not remove the need to seat the plug fully and check it. This guide has no failure-rate data for either connector.

Cables belong to the power supply

Modular power supplies let you plug in only the cables you need. The connectors on the component side, such as the graphics card or the motherboard, are standardized. The power-supply side is not. Corsair says each manufacturer is free to choose how the wiring is applied on that side, so you should never use one brand’s cables with another brand’s supply. It says doing so could be dangerous to you and your components.

Seasonic’s cable compatibility guide, updated in November 2025, goes further. It says pinouts often differ even between series of the same brand, lists which of its own series can share cables, and tells owners of an unlisted model to contact support first. It names component damage, fire hazards and a voided warranty as possible results of a mismatch. Our reading: use the cables supplied with your unit, or cables its maker lists for that exact model. A cable that looks right is not evidence that it fits.

Transient loads and what test reports show

Graphics cards and processors can raise their power draw very quickly. Hardware Busters, a PSU review site, describes transient response as how a supply’s voltage deviates and recovers during those shifts. Its ATX v3.1 test notes apply transient loads at several levels, up to 200% of rated load, and say that for supplies without a 12+4-pin connector the maximum applied load is 150%. Gimaxo did not read the ATX specification itself, so these are Hardware Busters’ descriptions of how it applies the tests, not the standard’s own wording.

Test labs publish reports for individual units. The Cybenetics report page Gimaxo read has sections for protection features, hold-up time and ripple measurements. Ripple is the small fluctuation that remains on the output voltage. Our reading: a report describes one unit as tested. Match the exact model and revision before you rely on it, and read the section that answers your question instead of the summary label.

Sizing from the card’s figure

Start from the graphics card maker’s figure. NVIDIA’s comparison page lists a Required System Power for each model. Its footnote says the minimum is based on a PC configured with a Ryzen 9 9950X processor, recommends a PCIe CEM 5.1 compliant supply, and adds that power requirements can differ with the system configuration. Our reading: treat the listed figure as a starting point for a system like the one NVIDIA describes. If your processor or settings draw more, check the processor maker’s published figures before you settle on a size.

When it is not worth it

• You are chasing a higher 80 PLUS level. The label describes efficiency only, so it does not tell you whether a supply suits your card.
• You have no test report for the exact model. This guide cannot say how that unit behaves. Read the maker’s documentation and warranty, and treat the unknowns as unknown.
• You plan to use extension or third-party cables. Gimaxo found no maker guidance on them in this pass. Ask your supply’s maker before you buy.

Before you buy

1. Open your graphics card maker’s page and note the power figure and the connectors it lists.
2. Check which cable or adapter that maker lists for your card, and that your supply can provide it.
3. Use only the cables supplied with the unit, or cables its maker lists for that exact model.
4. Look for a lab or review report on the exact model, and read the protection, ripple and transient sections.
5. Read the supply maker’s warranty terms.

To find out whether a new power supply would change your frame rate at all, start with our gaming PC performance guide.

Image credits

The photo in this guide is by Project Kei and is licensed under the Creative Commons Attribution-ShareAlike 4.0 International license (CC BY-SA 4.0). License text: https://creativecommons.org/licenses/by-sa/4.0/. The license notice is the one given on the photo’s page on Wikimedia Commons.

• “Full modular ATX power supply unit”, taken September 19, 2021. Source: https://commons.wikimedia.org/wiki/File:Full_modular_ATX_power_supply_unit.jpg

Changes made by Gimaxo: the file was resized and converted to WebP, and the site shows it cropped to fit the page layout. Nothing else was altered apart from removing embedded metadata. The adapted file is shared here under the same license, CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), and anyone who reuses it must keep the credit above and the same license. The rest of this guide is not covered by that license. The creator does not endorse this guide. Any brand name on the unit belongs to its owner and is not licensed by this notice.

Sources

Named here as plain text. Pages read on November 6, 2026.

• CLEAResult, 80 PLUS program details
• NVIDIA, GeForce graphics cards comparison page, with its footnote on required system power
• Corsair, “Evolving Standards: 12VHPWR and 12V-2x6”
• NVIDIA support, “Power Connector Update – GeForce RTX 4090” (updated 18 November 2022)
• Corsair, “Are PSU Cables Universal?”
• Seasonic, PSU Cable Compatibility Guide (updated November 2025)
• Hardware Busters, ATX v3.1 test notes in a PSU review (transient response)
• Cybenetics, PSU evaluation report page (report sections)