Load Testing
Test 1 (119.42W Load – Cold)
| Rail | Load | Voltage | Ripple |
| 12V | 4.93A | 12.32V | 17.8mV |
| 5V | 4.97A | 4.97V | 10.6mV |
| 3.3V | 10.15A | 3.35V | 7.4mV |
| −12V | 0A | −12.12V | 9.0mV |
| 5Vsb | 0A | 5.12V | 6.2mV |
| AC Power | 134.62% | ||
| Efficiency | 88.71% | ||
| Power Factor | 0.94 | ||
Test 2 (204.23W Load – Cold)
| Rail | Load | Voltage | Ripple |
| 12V | 10.09A | 12.37V | 20.0mV |
| 5V | 9.82A | 4.91V | 11.0mV |
| 3.3V | 9.9A | 3.33V | 7.2mV |
| −12V | 0.1A | −12.12V | 22.2mV |
| 5Vsb | 1.01A | 5.06V | 12.6mV |
| AC Power | 237.93W | ||
| Efficiency | 85.84% | ||
| Power Factor | 0.96 | ||
Test 3 (263.76W Load – Cold)
| Rail | Load | Voltage | Ripple |
| 12V | 14.76A | 12.30V | 22.4mV |
| 5V | 9.86A | 4.93V | 12.6mV |
| 3.3V | 10.09A | 3.33V | 7.8mV |
| −12V | 0.1A | −12.15V | 30.0mV |
| 5Vsb | 1.01A | 5.06V | 17.0mV |
| AC Power | 306.63W | ||
| Efficiency | 86.02% | ||
| Power Factor | 0.96 | ||
Test 4 (322.12W Load – Cold)
| Rail | Load | Voltage | Ripple |
| 12V | 19.58A | 12.24V | 23.4mV |
| 5V | 9.88A | 4.94V | 12.8mV |
| 3.3V | 10.09A | 3.33V | 8.2mV |
| −12V | 0.1A | −12.29V | 38.0mV |
| 5Vsb | 1.01A | 5.05V | 22.0mV |
| AC Power | 374.3W | ||
| Efficiency | 86.06% | ||
| Power Factor | 0.97 | ||
Test 5 (379.22W Load – Cold)
| Rail | Load | Voltage | Ripple |
| 12V | 24.34A | 12.17V | 31.4mV |
| 5V | 9.94A | 4.97V | 13.0mV |
| 3.3V | 10.09A | 3.33V | 9.0mV |
| −12V | 0.1A | −12.24V | 47.8mV |
| 5Vsb | 1.01A | 5.04V | 28.8mV |
| AC Power | 444.96W | ||
| Efficiency | 85.23% | ||
| Power Factor | 0.97 | ||
Test 6 (436.33W Load – Warm)
| Rail | Load | Voltage | Ripple |
| 12V | 29.11A | 12.13V | 39.4mV |
| 5V | 9.98A | 4.99V | 17.2mV |
| 3.3V | 10.06A | 3.32V | 9.2mV |
| −12V | 0.1A | −12.3V | 63.4mV |
| 5Vsb | 1.01A | 5.03V | 37.0mV |
| AC Power | 524.27W | ||
| Efficiency | 83.23% | ||
| Power Factor | 0.97 | ||
I have no idea how this power supply passed 80 PLUS certification. According to the official report, the Megapower 550 Elite was able to deliver the full 550W with an efficiency of almost 81%. However, my unit wouldn’t deliver 550W at all. When I asked for more than 440W, it shut down. The efficiency was also worse than what I would expect from an 80 PLUS certified power supply. During test 4, it was at just over 83%, but bear in mind that we do have 230V here. In the USA, the power supply would barely be managing 80% here, and would have been even less efficient if it had been able to deliver 550W.
The good news, though, is that the output performance was OK. Starting with the 12V rail, the worst-case scenario was 12.37V during test 2, which equates to 3.1% regulation. It dropped to 12.13V during test 6, which equates to a drop of 0.24V, or 2%. The 5V rail stayed between 4.91V and 4.99V, which equates to 1.8% regulation and a 1.6% rise. The 3.3V rail stayed at a pretty much constant 3.33V throughout the testing. Overall, it’s not perfect, but it’s still a pretty good result.
| Rail | Test 5 (379.22W) | Test 6 (436.33W) |
| 12V |  |
 |
| 5V |  |
 |
| 3.3V |  |
 |
| −12V |  |
 |
| 5Vsb |  |
 |
The ripple suppression is very good. The 12V rail maxed out at 39.4mV, the 5V rail at 17.2mV and the 3.3V rail at just 9.2mV. The other two rails were above half-spec, but still well within allowable limits.
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