I suppose this is very simple question for any physicist, but not for an 'electricity' expert.

Power = P = F.v;

thus a reaction force due the energy flow is unavoidably equal to:

F = P/v

and because of the fact, the 'electric energy' flows with a speed about c = 3e8 m/s, the reactive force should be:

P/c simply...

But now, let compare: what the electricity science says about this problem?

It says something like this: the electric current is a flow of electric charges, and because in a metal the electrons are flowing only, therefore the force of inertia of a wire (carrying the power) is equal to a mass of these moving electrons inside the wire, and these electrons move there with a speed about 1mm/s !