Energy conservation in laser operation involves the input of energy into a gain medium, which excites atoms to a higher energy state. When a photon stimulates these excited atoms, they emit coherent photons, but the total energy output is always less than the energy input. The initial energy to excite electrons comes from external sources, such as electrical discharges or pump lasers, creating a population inversion necessary for laser action. The emitted photons carry energy corresponding to the difference between the excited state and the ground state of the atoms. If the energy input ceases, the laser will stop functioning due to the depletion of excited electrons.