Net metering is a billing instrument addressing electric consumers who generate their own electricity by operating self-generation electricity systems (e.g. photovoltaic systems). Under a net metering system, consumers are entitled to feed excess electricity into the grid when generating more electricity than they need. The consumers meter measures both the electricity used and the electricity fed into the grid so that the consumers pay the “net” electricity use. Net metering schemes have been introduced in a number of countries, e.g. Denmark, Belgium, Australia, Brazil.