The program by default uses hydraulic grade as the basis for its hydraulic computations. Energy grade at any given point is then computed by adding the velocity head to the hydraulic grade. Because of this standard practice, energy discontinuities may occasionally occur, such as when pipe size decreases in the downstream direction, or pipe slope increases.

If you want the calculations to be based on the energy grade line you can change it with the Structure Loss Mode Calculation Option.

Flow discontinuities can also be responsible for energy discontinuities. Since a structure is analyzed based on a different system time than a pipe, a direct comparison of energy grades is not reasonable.