Energy conservation laws in classical electrodynamics
  There are three electromagnetic integrals of motion that can be interpreted as the energy. These are the background energy, the elastic energy and the integral in the torsion field commonly referred to as the energy of the electromagnetic field. The integral in the torsion field gains the meaning of the energy insomuch as it is concerned with the mechanical energy of a charged particle. 
Valery P. Dmitriyev