I think he wants to calculate some different components of the electrical energy, like current, voltage, power, energy and harmonics and rms and average values etc.
My advice is to build a data acquisition board with a microcontroller added to it. The board should be able to measure current and voltage that you'll work on. It should sample them fast and clear enough. For this, you may use current and voltage sense ICs/parts or you may design some circuit which uses proper resistors, amplifiers etc to sense these assets. Then you'll pass these values to a microcontroller and calculate the required components. For example you'll make a fourier transform and find the harmoncis. Or you'll sample the electricity for a given period and calcuate the rms value etc.