The voltage that a power supply can supply under load and the stability of that voltage might be the most important criteria on which we judge a power supply. Modern PCs involve nearly all of the power that they need from the 12 volt rail(s) from the power supply, which means that power supplies have to be able to offer a sufficient amount of power here, at the correct voltage. As stated before we tested in steps of 100 watts, and all 700W and 750W models turned out to be able to supply 700 watts, while all 850W models withstood our 800 watts tests. It is primarily interesting to look at the highest and lowest voltage that the power supplies offer at different amounts of load; after all deviations of more than 5% compared to 12 volt are not desired.
Unfortunately we see that a few power supplies do not perform well. The Be quiet! PurePower 9 CM 700W and the Cooler Master MasterWatt Lite 700W both drop down to 11.3 volts, while 11.4 volts is the bare minimum that is permissible. The Be quiet! PurePower 10 700W barely manages to achieve this minimum with 11.5 volts, while all other power supplies offer at least 11.7 volts under every circumstance. None of the tested power supplies show values that are more than 5% above 12 volts; the highest voltage that we measured was 12.33 volts with the FSP Raider 750W.
Of course we would like to see minimal deviation in the minimum and maximum voltage while keeping as close to 12 volts as possible. In this regard the Antec Edge 750W, Antec HCP Platinum 850W, Be quiet Dark Power Pro 11 850W, Fractal Design Edison M 750W, Silverstone Strider Gold S Series 750W, Super Flower Leadex Platinum 850W, XFX TS Series 750W and all of the tested models manufactured by Corsair, EVGA and Seasonic perform extremely well.