How to calculate the switching loss of an OR Gate?
This gives you a guideline: -



Every time the OR-gate output rises to "1" you can regard the capacitor (in the table above) being charged-up to the supply voltage. This takes energy (\$CV^2/2\$) and that energy is unrecoverable because when the OR output falls to "0" the capacitor is discharged. A small amount of heat is produced.

Along comes another "1" and you put energy into the capacitor only to lose that energy when the output goes low. So, if your Vcc is 3.3 volts then the energy injected into the capacitor is 114 pico joules. 

However, you do that 24,576,000 times a second hence the power is 2.81 mW or, the average current taken from the 3.3 volt DC supply is 0.85 mA.

It's a rough guide.