Not all of the generated power of a plant is necessarily delivered into a distribution system. Power plants typically also use some of the power themselves, in which case the generation output is classified into gross generation, and net generation.
Gross generation or gross electric output is the total amount of electricity generated by a power plant over a specific period of time. It is measured at the generating terminal and is measured in kilowatt-hours (kW·h), megawatt-hours (MW·h), gigawatt-hours (GW·h) or for the largest power plants terawatt-hours (TW·h). It includes the electricity used in the plant auxiliaries and in the transformers.
:Gross generation =  net generation + usage within the plant (also known as in-house loads)
Net generation is the amount of electricity generated by a power plant that is transmitted and distributed for consumer use. Net generation is less than the total gross power generation as some power produced is consumed within the plant itself to power auxiliary equipment such as pumps, motors and pollution control devices.  Thus
:Net generation =  gross generation − usage within the plant ( in-house loads)