What is the difference between energy line and energy grade line?

Answer 1

Difference between energy line and energy grade line
The line showing the total energy at any point in a pipe. The total energy in the flow of the section with reference to a datum line is the sum of the elevation of the pipe centerline, the piezometric height (or pressure head), and the velocity head. The energy grade line will slope (drop) in the direction of flow except where energy is added by mechanical devices. The line representing the elevation of the total head of flow is the energy line. The slope of the line is known as the energy gradient

Answer 2

The energy line represents the total energy at a specific point in a fluid flow system, including both pressure and velocity energy. The energy grade line represents the pressure energy at that point, and accounts for changes in elevation but not velocity. The difference between the two is the kinetic energy per unit weight of fluid.