Corsair RM550x Power Supply Review

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Efficiency, Temperature And Noise


Our efficiency testing procedure is detailed here.

Using the results from the previous page, we plotted a chart showing the RM550x efficiency at low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.

Under normal loads, the RM550x takes the lead from all of the other Gold-rated units. It loses only to the two Platinum units in our comparison graph. Although the deficit to Super Flower's Platinum platform is rather small, the passive Seasonic SS-520FL is way ahead with an impressive 1.68% difference.

Corsair's offering performs well under light loads, but most of the competing platforms are even more efficient. Without question, the efficiency champion in these situations is Cooler Master's V550S, which surpasses the 90% mark.

Efficiency At Low Loads

In the following tests, we measure the RM550x's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

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Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)Fan NoisePF/AC Volts
11.203A0.490A0.480A0.195A19.6169.61%00 dB(A)0.843
22.434A0.989A0.995A0.395A39.7380.44%00 dB(A)0.914
33.665A1.486A1.510A5.002A59.8384.76%00 dB(A)0.946
44.888A1.994A1.991A0.801A79.7787.05%00 dB(A)0.967

Under light loads, the RM550x operates passively, outputting zero noise. Efficiency drops below 70% in the first test, and in the second it barely manages to pass 80%. Only in the last two tests does this PSU start showing its potential, registering high enough efficiency levels.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load and 70 percent or higher with 1A or more of load.

We take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle. 

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Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

The 5VSB rail is highly efficient. We'd be even more impressed if we hadn't already seen the amazing performance of FSP's HG650, though.

Power Consumption In Idle And Standby

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Mode12V5V3.3V5VSBWattsPF/AC Volts

In the table above, you'll find the power consumption and voltage values of all rails except -12V when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Energy consumption at standby is very low with both voltage supply/input (115V and 230V).

Fan RPM, Delta Temperature And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed in RPM, and the delta between input and output temperature. The results were obtained at 36 °C (96.8 °F) to 48 °C (118.4 °F) ambient temperature.   

The next chart shows the cooling fan's speed (again in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 36 °C (96.8 °F) to 48 °C (118.4 °F) ambient temperature. 

The following graph illustrates the fan's output noise over the entire operating range of the PSU. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28 °C (82.4 °F) to 30 °C (86 °F).  

Acoustically, this PSU has more in common with its passive competition. If you need one of the quietest 550W power supplies available, the RM550x should be on your short list.

Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.

  • Dark Lord of Tech
    I just wish they would get the price down , these are a great lineup \ RX.
  • basroil
    From the performance it seems like CWT is finally something to consider... It's showing Leadex Gold/Seasonic levels of performance.
  • Dark Lord of Tech
    I love the RMX and RMI series , price just keeps me away from the purchase , very very solid.

    Knock a little off the price and these would fly out of warehouses.
  • William Henrickson
    They were on sale when new. I snagged an RM750i for $105 -w- shipping
  • Dark Lord of Tech
    Yeah the 550w should be about 79.99 to 89.99 , no rebates.
    Then I would grab a few.
  • JQB45
    Yeah the 550w should be about 79.99 to 89.99 , no rebates.
    Then I would grab a few.

    Corsair RMx 550W 80+ Gold Certified Fully-Modular ATX Power Supply

    $89.99 for the 650W version.


    Sorry thats with mail in rebates...
  • Dark Lord of Tech
    I don't do rebates , takes to long , and maybe you get it maybe you don't , I'll wait for a newegg drop.
  • Nintendork
    We really need more platinum/titanium PSU's at 300-500w. Most PC's stays near idle and with the efficiency focused gpu's/cpu's they rarely exceed 100w unless you tax them.
  • turkey3_scratch
    Plus companies often don't even send you the rebates, sometimes they just say it was too late or some other bull crap like that. I agree with Blackbird. I've been waiting for a review of the 550 RMx, and what I get out of this review is that it trades blows with the 550 G2 that saying one or the other is better is just silly and extremely nit-picky. They are both incredible. Both offer a 7 year warranty, as only higher-wattage G2s offer the 10 year warranty. They are just so close, that when it comes to picking the better one, the cheaper one is better, and the G2 is cheaper.

    I've actually quit including rebates in my pcpartpicker lists. They are a pain and I don't think they reflect the true cost of an item.
  • turkey3_scratch
    17653281 said:
    We really need more platinum/titanium PSU's at 300-500w. Most PC's stays near idle and with the efficiency focused gpu's/cpu's they rarely exceed 100w unless you tax them.

    I wish so, but unfortunately if this were to happen they would end up priced the same as any Platinnum/Titanium 650W unit. It's just the way it works. Quality low-wattage models are priced almost the same as the higher-wattage models. I would like to see something like a Titanium 250W model come out from Seasonic. Something like $40, fully modular. Will never happen, though.