An Energy Saving Certificate (ESC) is an electronic document that guarantees that, after carrying out an energy efficiency action, a new final energy saving equivalent to 1 kWh has been achieved. In this way, if an action is undertaken that results in an annual savings of 500 kWh, 500 ESC can be obtained.

This instrument allows energy savings to be monetized, recovering part of the cost of investments in energy efficiency (change of lighting, improvement of thermal insulation, renovation of industrial or domestic equipment, etc.), since the end user may receive a payment by selling the savings achieved for subsequent certification through the ESC System.