Low Number Of Efficiency Measurements
In a Tom's Hardware PSU review, we take into account 14 different load levels for our efficiency readings under high ambient temperatures, and over 1600 (which become more than 25,000 with data interpolation techniques) for temperatures in the 28°C to 30°C range. We're even thinking about increasing that range. In this way, we can accurately calculate a PSU’s overall efficiency score and easily compare it to similar models. In general, the more measurements you collect, the more accurate your result is.
| 80 PLUS Certification | 115V Internal Non-Redundant | 230V Internal Redundant | 230V EU Internal Non-Redundant | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Percentage of rated load | 10% | 20% | 50% | 100% | 10% | 20% | 50% | 100% | 10% | 20% | 50% | 100% |
| 80 PLUS | 80% | 80% | 80% | 82% | 85% | 82% | ||||||
| 80 PLUS Bronze | 82% | 85% | 82% | 81% | 85% | 81% | 85% | 88% | 85% | |||
| 80 PLUS Silver | 85% | 88% | 85% | 85% | 89% | 85% | 87% | 90% | 87% | |||
| 80 PLUS Gold | 87% | 90% | 87% | 88% | 92% | 88% | 90% | 92% | 89% | |||
| 80 PLUS Platinum | 90% | 92% | 89% | 90% | 94% | 91% | 92% | 94% | 90% | |||
| 80 PLUS Titanium | 90% | 92% | 94% | 90% | 90% | 94% | 96% | 91% | 90% | 94% | 96% | 94% |
The 80 PLUS program is significantly different. On all but the 80 PLUS Titanium certifications, it only takes into account efficiency under three load levels (20%, 50%, and 100% of the PSU’s maximum-rated capacity). In the Titanium tier, 80 PLUS also adds a 10% load test to its requirements. As expected, this low number of tests doesn’t clearly depict a test subject's overall efficiency. And to make matters worse, an OEM behaving badly can fool this methodology by sending hand-picked golden samples that are tuned to perform better under those specific load levels. This is far more difficult to pull off with a larger number of efficiency measurements under variable load levels.
Efficiency readings aren’t stable, meaning that there can be significant variations, especially under very low or very high loads. Lab-grade load testers might be able to apply a steady load for prolonged periods, but that doesn't mean the PSU will register exactly the same efficiency levels. Even the slightest change in temperature affects the performance of parts inside a power supply, resulting in load regulation and efficiency variations. Moreover, the active power factor converter (APFC) circuit can easily make a power analyzer’s readings go crazy under very light loads. Under such scenarios, the need for an advanced logging program that gathers all results, filters them, and provides an accurate average reading is essential.
MORE: How We Test Power Supplies
MORE: How To Choose A PSU