Power calculation for rectangular waveform in Cadence

Hi to all,

I'm trying to built simple power amplifier with cmos output. I need to calculate output power in tran analysis, usually I do it with dft function and rms value for signal.
For example for sinus we know:

Also, from wiki crest factor for rectangular waveform equal to 1.
Does it mean, that final equation for dft will be

?
If so, what will happen if duty cycle isn"t equal to 50% ?