[alfsch]

wers genau wissen will,
power wird ala spice so berechnet:

The circuit is run until steady state is sensed by the
simulator. This requires the SMPS macromodels to be
written with information on how to detect steady state.
Usually this is detected by noting when the error amp
current, averaged over a clock cycle, diminishes to a small
value for several cycles.
Then at a clock edge, the energy
stored in each reactance is noted and the simulation is run
for another ten clock cycles but now integrating the
dissipation in every device. At the clock edge of the last
cycle, the energy stored in every reactance is noted again
and the simulation is stopped. The efficiency is reported
as the ratio of output power delivered to the load by the
input power sourced by the input voltage after making an
adjustment for the change in energy stored in the
reactances. Since the dissipation of each device was also
noted, it is possible to look how close the energy checksum
is to zero.