Should we divide the power at 0Hz by two for Single-Sided Power Spectrum with FFT?
The factor of &quot;2&quot; comes from the contribution of the negative frequencies, which doesn't apply to DC.
A better way to plot this is to NOT multiply with 2 but plot the entire FFT range from -400Hz to +400Hz. There you will see three components: 1 W at DC and 0.25W each at -50Hz and +50Hz which is exactly what's happening here.
If you want to plot power spectrum one sided, you need to multiply by two EXCEPT for DC and Nyquist, which have no negative frequency equivalent.