$\textit{Complex Power}$, under sinusoidal conditions,
is the product of the phasor $\mathbf{U}$ representing the voltage between the terminals of a linear two-terminal element,
or two-terminal circuit and the complex conjugate of the phasor $I$ representing the electric current in the element or circuit.
Applicable units are those of quantitykind:ElectricPower
http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=31891
http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=131-11-39
$\underline{S} = \underline{U}\underline{I^*}$, where $\underline{U}$ is voltage phasor and $\underline{I^*}$ is the complex conjugate of the current phasor.