CMOS AND Circuit calculate power consumption
Since this is CMOS-type logic, most of the time only one of the p/n mosfet pairs is conducting which means (pretty much, ignoring leakage currents) no current is flowing.
The most power is therefore lost in the switching phase, when the mosfets switch roles (MOSFET1: conducting -&gt; nonconducting; MOSFET2: nonconducting -&gt; conducting).
In the following I will neglect the losses from both mosfets conducting at the same time when changing roles. Since you need to change the gate-source voltage of the mosfet to change the current flowing through it and the gate has a certain capacitance, you need a certain amount of charge to accomplish this change of gate voltage and therefore, current. This means that you will need a certain amount of energy for each switching cycle (E = Q_gate * abs(U_start - U_stop) = 0.5 * C_gate * (U_start - U_stop)^2 where the absolute value for  (U_start - U_stop) will be 4.9V or 5V in your case). 
So basically you need to figure out how many transistors get switched at what frequency to get the average power consumption (P = dE/dt = (n * 0.5 * C_gate * U^2) / T =  n * 0.5 * C_gate * U^2 * f where f is your switching frequency, n the amount of mosfets switched, U your supply = 4.9V/5V).