after some arduous testing, these are my findings:
if you decide to press the right side of the power button, you will need to apply a force of 78.45 kPa in order to successfully turn your phone ON or OFF.
if, on the other hand, prefer to use the left side of the power button, you will need no less than the pressure of 88.26 kPa to accomplish the same task.
keep in mind though, that these numbers may vary depending on the distance from the edge of the button. if the epicenter of your pressure is located at 3mm from the edge instead of 4mm the force will be slightly higher.
i hope you will find my findings useful in discovering the position of the button that best fits your needs. if you would like to know the exact pressure needed for a particular area of the button, just reply with the exact distance from its edges, and i'll be happy to fill you in.