Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
Efficiency, Temperatures And Noise
Efficiency
Using the results from the previous page, we plotted a chart showing the efficiency of the EDF550AWN at low loads and at loads equal to 10 to 110 percent of the PSU's maximum-rated capacity.
The Enermax unit's efficiency is high. But the digital platform fails to impress us. Seasonic's analog platform, used by both Seasonic and SilverStone in their passively-cooled power supplies, performed much better, showing that analog components with the proper design can still be highly competitive, especially compared to early digital platforms. After all, this is the first digital PSU from Enermax. Hopefully, experience that the company gathers from its design phase will help improve future digital units. Analog designs are much more mature, since they have been around for many years and engineers know lots of ways to tweak their performance. Inevitably, it will take some time until we see digital PSUs that definitively surpass their analog counterparts.
Efficiency At Low Loads
In the next tests, we measure the EDF550AWN'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 | 5 VSB | Power(DC/AC) | Efficiency | PF/AC Volts |
|---|---|---|---|---|---|---|---|
| 1 | 1.204A | 0.490A | 0.470A | 0.195A | 19.62W | 70.60% | 0.806 |
| 12.087V | 5.073V | 3.393V | 5.078V | 27.79W | 115.1V | ||
| 2 | 2.439A | 0.978A | 0.972A | 0.390A | 39.70W | 81.34% | 0.898 |
| 12.082V | 5.071V | 3.390V | 5.069V | 48.81W | 115.0V | ||
| 3 | 3.676A | 1.467A | 1.474A | 0.590A | 59.81W | 85.57% | 0.933 |
| 12.078V | 5.069V | 3.388V | 5.060V | 69.90W | 115.0V | ||
| 4 | 4.903A | 1.973A | 1.947A | 0.790A | 79.78W | 87.66% | 0.952 |
| 12.074V | 5.068V | 3.386V | 5.050V | 91.01W | 115.0V |
At light loads, the Enermax unit's efficiency is good. Even with a 20W load, it stays above 70 percent. The unit breaks the 80-percent mark in the second test with a 40W load, and in the next two tests, efficiency registers a nice boost. Without any doubt, this PSU is perfect for systems with low energy demands that spend long periods idle or with low utilization.
ZDPMS Efficiency Test Screenshots
Screenshots of the ZDPMS software below illustrate the four efficiency tests shown in the above table. The order of the screenshots is the same as the order of the tests.
The efficiency readings during the first and the third tests were accurate enough. However, in the other two tests, they were way off. Also, the voltage readings weren't as close to the real ones as measured on the connectors of the PSU using our equipment.
5VSB Efficiency
The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency 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 at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | Power (DC/AC) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.101A | 0.51W | 72.86% | 0.062 |
| 5.083V | 0.70W | 115.1V | ||
| 2 | 0.252A | 1.28W | 79.50% | 0.133 |
| 5.078V | 1.61W | 115.1V | ||
| 3 | 1.002A | 5.06W | 81.88% | 0.275 |
| 5.051V | 6.18W | 115.2V | ||
| 4 | 2.502A | 12.50W | 80.91% | 0.406 |
| 4.997V | 15.45W | 115.0V |
With 115V input, the 5VSB rail is highly efficient. Enermax does a good job here.
Efficiency is significantly higher on the 5VSB rail with 115V input than it is with 230V. The Enermax unit performs well; however, the Seasonic platforms once more manage to take the lead.
Power Consumption In Idle And Standby
| Mode | 12V | 5V | 3.3V | 5VSB | Power (AC) | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.085V | 5.086V | 3.397V | 5.085V | 6.93W | 0.372 |
| 115.1V | ||||||
| Standby | Row 2 - Cell 1 | 0.08W | 0.007 | |||
| 115.3V |
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).
At standby, the PSU shows low energy levels, and it passes the ErP Lot 6 2013 requirements easily.
Delta Temperature And Output Noise
The following chart illustrates the delta between input and output temperature. The results were obtained at 38 to 45 degrees C ambient temperature.
There is no cooling fan in this passive unit, so there is no noise output. We didn't notice any coil whine, either.
