Electromagnetic energy and power in terms of charges and potentials instead of fields (comments with reply)

In paper 6471A (see IEE Proc. A. vol.136, p.55-65 1989), C.J. Carpenter presented an alternative method of calculating the energy associated with an electromagnetic field. Instead of using the classical expression for the energy density given by u_f=¹/₂(E.D+H.B) (A) he assumes the expression u_c=¹/₂( rho phi +j.A) (B) where phi and A are the scalar and vector potentials respectively. The commenters point out that integral u_fdV and integral u_cdV are not equal, in general, although they are identical when the fields are not changing with time. The reply of the original author is presented.