P = V x I.
But also, V = I x R.
So substitute the second equation into first equation.
You will get P = I^2 x R.
I prefer P = I^2 x R as P = VI can be misleading at times...
especially when it comes to power losses in transmission cables.
The V to be used is NOT the voltage of the electricity being
transmitted, but rather, the potential difference across the
cables.
