Efficiency, Temperature And Noise
Efficiency
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.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed (RPM) | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.203A | 0.490A | 0.480A | 0.195A | 19.61 | 69.61% | 0 | 0 dB(A) | 0.843 |
| 12.122V | 5.020V | 3.315V | 5.013V | 28.17 | 115.1V | ||||
| 2 | 2.434A | 0.989A | 0.995A | 0.395A | 39.73 | 80.44% | 0 | 0 dB(A) | 0.914 |
| 12.117V | 5.018V | 3.313V | 5.007V | 49.39 | 115.1V | ||||
| 3 | 3.665A | 1.486A | 1.510A | 5.002A | 59.83 | 84.76% | 0 | 0 dB(A) | 0.946 |
| 12.112V | 5.017V | 3.312V | 5.002V | 70.59 | 115.1V | ||||
| 4 | 4.888A | 1.994A | 1.991A | 0.801A | 79.77 | 87.05% | 0 | 0 dB(A) | 0.967 |
| 12.107V | 5.015V | 3.310V | 4.996V | 91.64 | 115.1V |
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.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.101A | 0.51 | 77.27% | 0.067 |
| 5.069V | 0.66 | 115.1V | ||
| 2 | 0.252A | 1.28 | 81.01% | 0.147 |
| 5.064V | 1.58 | 115.1V | ||
| 3 | 1.002A | 5.06 | 81.22% | 0.324 |
| 5.045V | 6.23 | 115.1V | ||
| 4 | 3.002A | 14.99 | 79.65% | 0.424 |
| 4.994V | 18.82 | 115.1V |
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
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.130V | 5.026V | 3.319V | 5.026V | 7.75 | 0.487 |
| 115.1V | ||||||
| Standby | 0.05 | 0.005 | ||||
| 115.1V |
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.