The first PSU we received from BFG for our tests was dated the 9th week of 2008 (you can learn the manufacturing date from the first four digits of the serial number glued to the PSU label). It turned to be a presale version that didn’t make it into shops due to one problem. Its output voltage ripple was too high.
PSU made on week 9
Indeed, the +12V rail is calm but the pulsation on the low-voltage rails is nearly twice as high as the permissible maximum of 50 millivolts even though the load on those rails was only 65 watts in the test (the remaining 700 watts with something were provided by the +12V rail).
It is nice that the manufacturer had been aware of the problem and suggested to replace the defective PSU before I reported the problem to them. According to BFG, there are additional smoothing capacitors in PSUs manufactured after the 15th week of 2008. It is the improved version that comes to retail.
PSU made on week 15
Alas, the problem didn’t vanish completely. The oscillogram shows that the output voltage ripple on the +5V and +3.3V rails is still above the permissible maximum although the short spikes are now much smoother.
The PSU shows good cross-load characteristics. The voltage on the +3.3V rail is the only one to exceed a 3% deflection but this happens only at a near-maximum load and when the load distribution is shifted towards the low-voltage rails, which is virtually impossible in a modern computer system.
The fan speed management is quite interesting here. There are a few bends in the graph. The fan starts out at a speed of 900rpm. It is quiet then, but not absolutely silent. The fan begins to speed up at a load of 200W and accelerates to 1100rpm, producing distinct noise. At loads above 550W the fan’s speed quickly grows to the maximum of about 1800rpm.
Thus, the BFG ES-800 is a quiet but not silent power supply. It is satisfactory in terms of noise at low and medium loads, but you may want to consider other models if you want silence.
Efficiency is supposed to be the strong point of the ES series. It is good indeed. The PSU is 80% efficient at 10% from maximum load. The maximum efficiency is a superb 88%. The efficiency drops to 75% at a load of 50 watts, the minimum load in our tests, and this is somewhat better than 70% that most other PSUs show. On the other hand, the 5% difference at such a low load amounts to only 2.5 watts of saving.
The power factor graph is interesting, too. The power factor is as low as 0.65 at low loads, and oscillograms show that the PSU consumes the current with each second half-wave of the supply voltage. This may be the result of an adaptation of the PFC device for achieving maximum efficiency.
The BFG ES-800 is an ambiguous product overall. If it were not for the exceedingly high output voltage ripple, which is present even in the newer version of the PSU, this model might be called good as it provides a good selection of connectors, has a quiet fan, and offers stable voltages. Its efficiency is the most advertised quality of the ES series, and it is indeed high in comparison with other modern PSUs. However, the advantage over high-efficiency PSUs from other brands, including some models covered in this review, is not large at all.