This high-wattage power supply is the top of the line of our fully modular multi-output ATX power supply family, that was pioneering in obtaining the industry’s first 80 Plus® Gold certification. Its newly improved Hybrid Fan control circuit employs hysteresis through an innovative IC, which automatically adjusts the fan mode and its speed according to the ambient temperature level. Reducing the number of on/off cycles of the fan further improves energy utilization and prolongs the lifespan of the system. This recently upgraded member of the premium X-series product family boasts true class leading performance and build quality.

SKU: SS-1250XM2 Active PFC Categories: ,

80 PLUS®Gold

Seasonic was the forerunner of creating the very first 80 PLUS® Gold certified power supply on the market and since that time it has built a very popular Gold series lineup that covers a full power range of power supplies with impeccable performance and efficiency. The highly efficient 80 PLUS® Gold certification guarantees greater than 87 %, 90 % and 87 % efficiency at 20 %, 50 % and 100 % operating loads, respectively. The clear advantage of buying a power supply with 80 PLUS® Gold rating is the fact that the less energy gets wasted during power conversion, the lower the operating costs will be for the user.

The New Seasonic S3FC Fan control

XP3 XM2 fan chart

What is S3FC?

The industry’s first, Seasonic patented, advanced three-phased thermal control balances between silence and cooling. This Hybrid Silent Fan Control functions in three operational stages: Fanless Mode, Silent Mode, and Cooling Mode. In addition, there is a switch provided to allow for manual selection between the Seasonic S2FC (fan control without Fanless Mode) and the S3FC (fan control including Fanless Mode).

New! Power saving by hysteresis

Hysteresis is achieved by an additional fan control IC, which optimizes how frequently the fan switches on and off. At 25 °C ambient temperature the fan turns on when the load rises above 35 % (±5 %) and it turns off when the load drops below 25 % (±5 %). Due to this lag in response the fan switches on and off less frequently, which reduces noise and power loss in Fanless Mode and Silent Mode.

Fan Type Sanyo Denki-01

Sanyo Denki Fan

The world-renowned Sanyo Denki ball bearing fans are made of the highest quality components to ensure ultra-low noise performance. The fan’s perfect balance and even rotations are achieved via the use of spoon-shaped, high-density plastic fan blades that are finished off with smoothed leading edges. Sanyo Denki fans are known for their strict tolerance ball bearings and precision copper axels. Instead of the industry standard of two balancing points they use three points to strengthen the mount and further stabilize the blade.

Dual Copper Bars-01  

Dual Copper Bars

Due to their increased diameter, pure copper bars carry high current much more effectively than the traditional copper strips. If the goal is to achieve high quality power conversion with stable power output and minimized loss, it is very important that power conduction in the high wattage area remains extremely efficient, because it also reduces impedance and minimizes voltage drop as the load increases.

Japanese Capacitor-01

105 °C Japanese Capacitor

Premium quality Japanese capacitors with 105 °C rating increase overall reliability and extend product life.

Stable Voltage Regulation-01 

Stable Voltage Regulation (2 %)

Improved voltage regulation stays well within Intel’s specifications to ensure smooth operation and protect all system components.

7 Years Warranty-01

7 Years Warranty

Our commitment to superior Seasonic quality.

Specifications are subject to change without prior notice.
Note: Since the beginning of 2015, Seasonic has implemented changes in its retail box design and modular cables are now packed in a black cardboard box.

AC InputVoltage: 100 V - 240 V
Current: 15 - 7.5 A
Frequency: 50 Hz - 60 Hz
DC OutputRail+3.3 V+5 V+12 V-12 V+5 VSB
Maximum Power25 A25 A104 A0.5 A3 A
150 W1248 W6 W15 W
Total continuous power1250 W
X-1250 Technical Specifications
Form FactorIntel ATX 12 V
Dimensions150 mm (W) x 190 mm (L) x 86 mm (H)
Fan InformationFan Size120 mm
Fan ControlNew Seasonic S3FC
Fan BearingDouble Ball Bearing
Life Expectancy70,000 at 40 °C, 15 % - 65 % R.H.
Cable InformationModularityFully Modular
Cable typeFlat black cables
Electrical FeaturesOperating Temperature40 °C
MTBF @ 25 °C, excl. fan150,000 hours
AC InputFull Range
ProtectionOPP, OVP, UVP, OCP, OTP, SCP
Safety and EnvironmentalSafety and EMCcTUVus, TUV, CB , BSMI, CCC, CE, FCC, C-tick
Environmental ComplianceEnergy Star, RoHS, WEEE, ErP Lot 6, REACH
Warranty7 Years
Packaging information
Units per carton4
Individual carton size385 (L) x 130 (W) x 195 (H) mm
Shipping carton size545 (L) x 215 (W) x 405 (H) mm
Specifications are subject to change without prior notice.

ConnectorConnector CountLengths
MAIN-POWER-24-20-PIN-A1610 mm - modular
PCIE-8-PIN-A24/8 Pin - 650 mm- modular
8 Pin - 650 mm- modular
PCIE-6-8-PIN-1-A10550 + 100 mm - modular
550 + 100 mm - modular
550 + 100 mm - modular
550 + 100 mm - modular
550 + 100 mm - modular
SATA-5-PIN-A14400 + 120 + 120 + 120 mm - modular
400 + 120 + 120 + 120 mm - modular
400 + 120 + 120 + 120 mm - modular
300 + 120 mm - modular
PERIPHERAL-4-PIN-A5400 + 120 + 120 mm
300 + 120 mm
FDD-4-PIN-1-A1101 mm
Specifications are subject to change without prior notice.





Enlace Hardware | 5 Stars

November 26, 2014

“…es la mejor inversión que se pueda adquirir si necesitas una unidad con este nivel de potencia…”

(Read More)

JonnyGURU | Recommended 9.6

August 10, 2014

“… if you came to this review wondering if Seasonic was still leading the industry… oh, hell yes.”

(Read More)

PC Perspective | Gold Award

July 30, 2014

“…you have one very good power supply.”

(Read More)

KitGuru Best of 2013

January 2, 2014

“El Classico”, “The Seasonic X-Series 1,250w PSU is the Terminator of power supplies, it doesn’t eat/drink/sleep/rest/make mistakes – it just delivers.”

(Read More)

HardOCP | Editor’s choice

November 13, 2012

“Like a good Swiss watch everything moved just about perfectly and looked good in the process.””…a unit that features truly excellent build quality, voltage regulation, noise profile, transient load results.” “The Seasonic X-1250 is quite simply an excellent power supply and an excellent value.”

(Read More)

Gamezoom | ULTRA gamezoom Award

October 16, 2012

“Das Seasonic X-1250 punktet auf der ganzen Linie! Technik, Verarbeitungsqualität und Kühlkonzept lassen keinen Platz für Kritik

  • top Leistung
  • einwandfreie Technik
  • voll modulares Kabelmanagement
  • sehr hoher Wirkungsgrad
  • Verarbeitungsqualität
  • viel Power (Watt)
  • leiser Lüfter (Semi-Passiv-Kühlung)
  • zahlreiche Anschlüsse

(Read More)

PC Perspective | Editor’s choice

October 10, 2012
  • 1,250W continuous DC output
  • Very good efficiency across a broad range of loads (80Plus Gold certified)
  • Excellent voltage regulation
  • Very low AC ripple even at 100% load
  • Silent, fanless operation at lower power levels
  • Quiet operation at mid to upper power levels
  • Single +12V output can deliver up to 104A/1248W
  • Eight PCI-E connectors (6/8-pin)
  • Active PFC with universal AC input
  • Sleeved cables with gold-plated connectors”

(Read More)

JonnyGURU | Recommended

September 25, 2012

“First unit ever to throw down a 0% voltage regulation number on the 5V output…

  • Exceptionally stable regulation on all outputs.
  • Fully modular.
  • Easily passed efficiency certifications in both hot and cold tests.
  • Extremely low ripple.

(Read More)

Kitguru | Must Have

August 21, 2012

“Technically, the DC to DC Seasonic design is exemplary, combining very high levels of efficiency with rock solid voltage regulation.”

(Read More)

Easycom | Quality Award

July 29, 2012

“X-1250 is an excellent solution for top configuration with 4 top VGAs and any most powerful processor.”

(Read More)

Easycom | High Performance Award

July 29, 2012

“Extreme overclockers will also like this PSU since his Overload test shown stable work at 1650W. At the same time this PSU has hybrid cooling system making it fanless at low loads.”

(Read More)

The Overclock Hole | Gold Award

June 13, 2012
  • Connettori placcati oro
  • Interno di lodevole qualità
  • Tensioni stabilissime”

(Read More)

The Overclock Hole | Best Choice

June 13, 2012

“Finita questa serie di test possiamo definirci soddisfatti di un prodotto che, ancora inscatolato, sapevamo non ci avrebbe deluso!

  • Prezzo adeguato
  • Efficienza molto elevata
  • Notevole numero di connettori”

(Read More)

Next Hardware | 5 Stars

May 31, 2012

“Veramente sorprendente, inoltre, è stato il risultato della prova di sovraccarico che ha catapultato il Seasonic X-1250W all’apice di una ipotetica classifica dedicata agli alimentatori per overclock estremo.”

(Read More)