We present a fit formula for the excess internal energy of the one-component plasma in the fluid phase that was obtained from the analytic solution of the mean spherical approximation for charged hard spheres in a uniform neutralizing background by utilizing a new relation for the effective packing fraction. Our results are in much better agreement to recent Monte Carlo data for strong coupling, I? 2 1, than previous results from similar calculations, and extend down to the Debye limit, l? -+ 0.