You can measure the electric power (kWh), which is used in machining process (one machine).  

The machining cost involve:

Tools: 1% to 5%

Lubricants: up to 16%

Human resources: aprox. 35%

Cost of machine tool per hour: reposition value of the machine tool divide by 10.000 hours.

Mean energy cost by machine: the value that the factory pay about energy divide the number of machine tools that the factory have working. In this case, is very important to take the use factor of each machine.

There ids a need to calculate the energy required to maintain the machining process and the energy required to operate the machine tool.

Since the energy consumption is not a stable process, the energy cost can be averaged from the machining stuff of a whole day or a whole week.

Power will be vary based on voltage ,current and power factor.

First power is to be calculated for  one hour duration and then you need to calculate the output based on cycle time for one hour.

Energy consumption /part = total power consumption in kw for one hour÷( total output per hour )

Energy consumption  cost per part = energy consumption in hr /part ×( cost of energy consumption per hour ).

Finally you can add this cost to energy consumption cost to product conversation cost.

Regards

KANNAN.V.K

many thanks to all of you for these beneficial answer, really help me