We’ve got a characteristic picture with the +12V voltage: it is stable within the load range typical of modern PCs but fluctuates when there’s very high or low load on the +3.3V and +5V rails.
I’ve mentioned the suspiciously low load capacity of the +5V rail above and indeed this voltage is very unstable. It deflects by 5% from the default level even at 40-50 watts. Both of our reference configurations this PSU is able to power up are in the 4% zone.
The +3.3V voltage isn’t perfect, either, but deflects no more than by 3% in the typical load range.
By the way, the PSU could only yield about 80 watts instead of the specified 120 watts across the +3.3V and +5V rails combined without violating the voltage stability requirements.
Overall, this performance is satisfactory, but you can find PSUs with more stable voltages in the same product category.
Output Voltage Ripple
The high-frequency ripple is close to the permissible limits on the +12V rail. The +3.3V and +5V rails are more stable, but there are occasional voltage spike up to the limits described by the industry standard.
The same goes for the low-frequency ripple. The +5V voltage is the most stable one, lacking any voltage spikes.
Temperature and Noise
The PSU is cooled by a Yate Loon fan (D12SM-12) that has a rated speed of 1650 RPM. We’ve seen the same fan in the Cooler Master RS-400.
The start speed is lower at 1000 RPM than that of the Cooler Master but the fan accelerates linearly right from the start, reaching 1500 RPM at a load of 350 watts. The fan doesn’t speed up much after that, keeping the difference in temperature between the incoming and outgoing air low at 7°C.
The PSU isn’t silent, yet not uncomfortable.
Efficiency and Power Factor
Although the Antec lacks even basic 80+ certification, its specs are close to meeting the Bronze version of that standard. It is over 85% efficient at loads of 80 to 310 watts and about 82% efficient at full load.
The power factor is lower than usual for active PFC, but that’s unimportant for home users.
The standby source copes with its job well, keeping its voltage within 2% of the required level.
Being rather efficient, the Antec VP450P has problems with the +5V rail and isn’t very quiet. Its price seems to be too high. The higher-wattage and more advanced Antec HCG-520 is but slightly more expensive yet superior in every parameter whereas competitors’ products of comparable wattage and efficiency are cheaper and free from the mentioned downsides.