Although the efficiency of the Seasonic G 550W power supply is extremely stable and high while the unit is powered from a 110V AC source, the unit failed to meet the 80Plus Gold certification limit of 92% at half load while it was being powered from a 230V AC source. Nevertheless, the efficiency of this product remains very high, although it appears to be optimized for markets with 90V-120V AC grids.
The mediocre power output and very high efficiency allow for the Seasonic G 550W power supply to generate minimal amounts of heat. Thus, it is no wonder that the thermal performance of the particular unit is astonishing, with the unit getting barely warm under maximum load and the temperature differential between its intake and exhaust is a mere 4.5°C.
The high efficiency of this power supply, in conjunction with the good design and sizable heatsinks, allows for the fan to maintain a low rotational speed, keeping noise down to a minimum. Thus, the Seasonic G 550W will remain entirely silent even if heavily loaded, with the noise coming from the fan getting clearly discernible only of the load exceeds 90% for prolonged periods of time.