Being the first SFX PSU reviewed on Overclock3D thus far, it does make it slightly difficult to draw a conclusion on its performance in relation to any alternatives on the market. However, as much as I told myself not to compare the be quiet! SFX Power to the likes of an ATX PSU, it has become increasingly obvious throughout the testing that the unit is easily capable of competing with some of its full-sized counterparts.
Take for example the efficiency. At anything between 200-300w load the unit managed a highly respectable 85%. This only dropped down to 83% at other load levels, and even when run well above specification at an impressive 420w in Test 7, still managed to keep its chin up at 82.84%. This will play an important part in keeping energy bills to a minimum, especially when HTPC's and SFF Home/NAS servers tend to be left on 24/7.
Moving on to the voltage stability there's very little to be concerned about here either. The +3.3v and +5v rails may not have been quite as stable as some of the 350W full-sized ATX PSU's I've tested in the past, but with voltages ending up at 3.31v and 4.92v at full load, you really cant complain. The +12v rail was a bit of an odd ball, starting at 11.92v and actually increasing to 11.96v as a larger load was applied. This would tend to indicate that the voltage regulation on the PSU is overcompensating for the load and potentially reducing the maximum power output of the PSU at the top-end. However, with the unit managing to hold a 420w load in the testing this certainly wont pose any problem to those looking to get a full 350w out of the unit.
The only area that the be quiet! SFX Power failed to deliver (which is a bit ironic given its name) was in the noise output. At anything up to around 75% load the unit was perfectly silent. However on pushing closer to the PSU's maximum output, the 80mm fan speed increased significantly bringing with it the annoying pitched squeal that only 80mm fans are capable of. By 100% load the fan could easily be heard above the din of the PSU testing equipment which leads me to believe you wouldn't want your HTPC / SFF PC to be in the same room as you when this PSU is running flat out.
- Efficient operation for such a small unit
- Reasonable voltage stability in the 'normal' tests T1-T4.
- Sleeved Cables and Black finish make it good looking for an SFX unit.
- Ripple was surprisingly good.
- 420w max output!
- Didn't like the cross-load tests.
- Noisy approaching full load.
Although the be quiet! SFX Power is far from perfect, being able to fit such a stable and efficient PSU into a Small Form Factor casing is worthy of award. For this reason the be quiet receives our recommended award.