Seasonic Vertex GX-1200 PSU Review

The Seasonic Vertex GX-1200 offers high build quality, good performance, silent operation, and ATX v3.0 and PCIe 5.0 compatibility. How it fares though, against competiting offerings? Read the full review to find out. 

The Seasonic Vertex GX-1200 is included in my best ATX v3.0 & PCIe 5.0 PSU picks article.

The Seasonic Vertex GX line includes four members with capacities ranging from 750W to 1200W. All models of the line are ATX v3.0 and PCIe 5.0 ready and are supported by an extended, ten-year warranty. Seasonic has a solid reputation in the PSU market, and the Vertex line addresses the mid-segment, with the Prime models on top of them and the Focus models below. The Vertex GX-1200, which I will evaluate in this review, is a strong unit capable of handling an RTX 4090 paired with a power-hungry CPU, like the Intel i9-13900K(s). Given that the RTX 4090 can exceed 600W in power spikes and 600W in sustained power, and the 13900K is close to 370W sustained at stock speeds, it is better to have a 1200W PSU for such a combination to have enough room.



With 160mm depth, this is a compact PSU, given its capacity, so you won’t have any compatibility issues with standard ATX chassis. Thankfully the PSU’s casing is large enough to accommodate a 135mm fan, which utilizes a fluid dynamic bearing for increased reliability and lower noise output.


Technical Specifications:
  • Manufacturer (OEM): Seasonic
  • Max Power: 1200W
  • Cybenetics Efficiency: [115V] Cybenetics Gold (87-89%)
  • 80 Plus Efficiency: Gold
  • Noise: Cybenetics A- (25-30 dB[A])
  • Compliance: ATX v3.0, EPS 2.92
  • Operating Temperature (Continuous Full Load): 0 – 50 °C (derating from 100 % to 80 % from 40 °C to 50 °C)
  • Alternative Low Power Mode support: Yes
  • Power 12V combined: 1200W
  • Number of 12V rails: 1
  • Power 5V + 3.3v: 125W
  • Power 5VSB: 15W
  • Cooling: 135mm Fluid Dynamic Bearing Fan (HA13525H12F-Z)
  • Semi-Passive Operation: ✓ (selectable)
  • Modular Design: Yes (Fully)
  • High Power Connectors: 2x EPS (2x cables), 3x PCIe 6+2 pin (3x cables), 1x PCIe 12+4 pin (600W)
  • Peripheral Connectors: 18x SATA (5x cables), 3x 4-pin Molex (single cable)
  • ATX Cable Length: 620mm
  • EPS Cable Length: 710mm
  • 12VHPWR Cable Length: 750mm
  • Distance between SATA: 150/160mm
  • Distance between 4-pin Molex: 125mm
  • In-cable capacitors: No
  • Dimensions (W x H x D): 150 mm x 85 mm x 160mm
  • Weight: 1.96 kg (4.32 lb)
  • Warranty: ten years
  • Street price (excluding VAT): $296

Power Specifications

Rail 3.3V 5V 12V 5VSB -12V
Max. Power Amps 25 25 100 3 0.3
Watts 125 1200 15 3.6
Total Max. Power (W) 1200
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16 thoughts on “Seasonic Vertex GX-1200 PSU Review

  1. Massive coil whine on 3 Gx 1200 units when pc is at idle or when pc is off.


    There are posts about this issue on reddit, youtube and tomshardware.
    I never had such issue with psu it was so annoying, i returned my old non atx3.0 psu and its quiet again.

    I guess there are some new atx 3.0 parts inside causing thiss issue maybe.

    1. I have used several of them in my test systems with zero coil whine. I’ve even taken noise measurements close to 15 dBA with one of them in operation, without the fan spinning. Coil whine is due to lots of factors, not only the PSU.

  2. Nice review as usually by Hardware Busters! My previous psu was also Seasonic, I bought this for the new atx 3.0 standard specs. Great psu from Seasonic leader. Powerful and silent. It’s really the heart of your system. Mine, no coil whine. I was lucky and I bought it for 240€. At this price there is nothing better in atx 3.0 series. Seasonic quality, no worries for at least 10 years. Once Seasonic, for ever Seasonic.

    Ευχαριστώ Άρη για άλλη μια φορά.

    1. Thank you very much for looking into this issue, i never had such annoying high pitch sound on any psu ever like this Gx. For this build i went with seasonic vertex gx 1200 cause of quality i paid 340 euros but was dissappointed and returned it after 10 days i hoped for the noise to go away but nothing.
      And the crazy thing is that when pc is off and switch off but power cable still in it still whines thru whole night to the point that i though that all of a sudden i got tinitus in ears.

      Now im 3 weeks without psu im interested in be quiet 12m at 200e for my 4090/7700x hope thats ok psu.
      Again thank you for your time and work.

  3. Coil whine on mine also, buzzing like sound so i put it under my desk but when i turn off my pc its still buzzing and i can hear it its like electric buzz for 5 or 6 seconds and then again after cca 10 seconds and thru whole night its insane.
    I tried erp mode in bios but still the same.

    32gb ram

    1. Hm, this starts to get weird. I will discuss with Seasonic and I will probably remove it from my best PSU’s page. Problem is that currently I am at Computex, with not much time to work on the site.

  4. Greetings,

    I would like to ask a question if I may. For the short circuit protection (SCP) feature of PSUs, does it only work when our house is grounded and it is useless when the house is not grounded?

    Many thanks

  5. My GX 1000 also suffered obvious coil whine. There is a thread on Tomshardware where multiple GX users from a couple months back had noticeable coil whine and electrical crackling/buzzing sounds, sent their units back.

    I had to do the same. The frequency was grating, worst when the machine was idling or near idling, which is much of the time. Didn’t matter if it was in Eco with the fan off or turned on. Pretty easy to hear even above six case fans and an AIO pump when I was two metres away. I felt this was a premium product and would be better.

    I had an 8 year old EVGA Supernova P2 850W lying about I knew was good, swapped that instead and it’s dead silent. Have to put my ear within 20 centimetres to the exhaust of this EVGA unit in eco mode with the fan off to hear anything at all. Kinda sad for the Seasonic. It cost more than twice as much as the platinum EVGA. Yes it’s 8 years later and yes it’s ATX 3.0 but I was disappointed to see these reports of GX coil whine and experience it for myself.

      1. Does Seasonic still send review units directly from places like Newgg or Amazon? If so getting a “golden sample” seems quite rare.

  6. I have a Vertex GX-850 and haven’t had any coil whine. Stability in my old 4770K with RX6700XT is great. Even when pushing the GPU and CPU to full load the semi-passive mode keeps the PSU silent.

  7. Can confirm, cricket like noise on my gx 1000w
    And coil whine at idle or when browsing the web in games its very quiet.

    Rtx 4080
    32gb ram

    1. I just talked to Seasonic and they told me that they will look into this ASAP! Because several users already reported this in these comments.

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