Power for an electrical system is relatively easy to determine.
Power in watts [J /s ]
Voltage in Volts [J / C ]
Current in Amps [ C / s ]
P = V x I
But what is power?
Power is energy consumed or release in a given quantity of time.
Power is different from energy as energy is conserved meaning it cant be created or destroyed.
Power can be increased or reduced by altering the amount of time the energy is exerted over.
In the normal mechanical world energy is either potential or kinetic.
Ek = 1/2 m * v²
Ep = mgh
Etot = Ep + Ek
If we consider a ball being raised 1 meter of the ground in a period of 2 seconds and then dropped to the ground reaching the ground in 0.5 seconds, the balls combination of potential and kinetic energy levels remain the same.
However the ball has gained power by expending its energy in a short period of time. this is the subtle difference between energy and power.
Only 1/4 of the power released was used to raise the ball.
Power is simply how quickly energy is stored or expended.