Power requried for M-ary modulation schemes
QPSK (quadrature phase shift keying) uses a modulating signal that produces no discernible change in amplitude (or power) because the 4 modulation amplitudes are held constant i.e. they are all on the circumference of a circle: -



This results in a time domain waveform typical of below: -



You can even take this further to 8-psk: -



So, the basic power remains the same for any m-ary purely-PSK system. However, there are variations and these have similar constellation patterns but there is amplitude modulation as well: -



Given that 4 out of the 16 bit combinations are centred further out than the others could mean the average power is greater but, there are also 4 bit combinations that are smaller than the others two so, given that these differences cancel out over time, you could argue that the net power is the same.