How about developing a PlugMote? [solution]

[perky]

As Tom says, power is dependent on 'power factor', i.e. the phase of the current wrt the voltage. If you can measure current and voltage then you can calculate power.
Mark.

[Roger2016]

Power factor, so basic Amps * Volts = Watts correct. 

to complicate things,  I'm running a Variable Frequency Drive (VFD) to adjust spindle speed.  It's 220V single Phase input and 3 phase output to the motor, so I could measure before the VFD or after the VFD.  Also the frequency I'm running will affect the load.  If I'm running 20Hz my spindle will stall way easier than if I'm running 100Hz, so to be useful I should somehow include Hz into the calculation.  I should also measure spindle RPM to see if i'm loosing RPM.  Nothing is ever easy!

[perky]

Just to be clear, power is instantaneous volts times amps, and total power will need to be averaged over a complete cycle.
Mark.