Capacity and voltages
Other than the two Huntkey CP power supplies, all of the PSUs in this test are able to supply the power they're advertising. The 300 and 350 watt PSUs made it through our 300 watt test and the 400 and 450 watt power supplies made it through our 400 watt test.
Being able to deliver the full capacity is one thing, be able to do it efficiently is just as important. According to ATX specifications they can deviate up to 5 percent, which means that values below 11.4V or above 12.5V can cause instability. So the closer to 12.0, the better. For the 5V line the voltages should be between 4.75 and 5.25V.
In our 300W test there are two PSUs that fall short of this, the Huntkey CP 350W (11.43 V) and the Chieftec Nitro 2 450W (11.22 V). That last one falls quite far below 11.44 volt at 400 watts, and the Corsair CX430 V2 did the same. Please note: a 400 watt test consists of 350 watts on the 12V rails and 50 watts from 5V and 3.3V.
On the 5V and 3.3V lines there were no variances in excess of 5%, but the closer the voltages are to what they should be, the better.