In recent years, the reliability of the power supply system has become urgent. A break in electricity supply, the cessation of electricity supplies of the same duration in different consumer enterprises causes a different severity of adverse economic consequences. The damage to a particular consumer of electrical energy is determined by direct losses and unrealized consumer capabilities in the process of its functioning. The article considers approaches to determining the damage from the unreliability of the power supply system, certain components of the energy damage. In the author’s opinion, this direction is promising for further research taking into account the priorities of the state policy in the field of energy efficiency and energy saving.