Q. How do I know if my power supply is regulated?

Answer

The supply is almost probably regulated if the output is stable to within 1% over the load range. For a controlled supply, percentages above 5% are likely to be questionable. The output voltage of regulated supplies is actively maintained at a constant level across a broad range of load currents. Supply ripple will be minimal if proper regulation is in place. Anything above 100 mV should be questioned. This is true whether or not there is a full supply. If the voltage is not regulated, it may have a few volts of ripple, or more in the loaded scenario. Whether or not the supply is regulated is secondary to the behavior of its output voltage under different loads.