Generally, at no load or light load, the power factor is relatively low. In such conditions, although the active power is low, the reactive power and input current is quite high, which results in high measured current using a multimeter. In order to accurately measure the active power, the RMS input current, RMS input voltage, as well as the distrotion and phase shift between V and I curves should be measured (with a powermeter, or an oscilloscope).
If only measuring V and I RMS values, the result is the apparent power, which comprises real and reactive power. Some models may require to use the Remote Off function to achieve low no load power consumption.