Practices that enable or aid self-sustainability include autonomous building, permaculture, sustainable agriculture, and renewable energy. The term is also applied to limited forms of self-sustainability, for example growing one's own food or becoming economically independent of state subsidies. The self-sustainability of an electrical installation measures its degree of grid independence and is defined as the ratio between the amount of locally produced energy that is locally consumed, either directly or after storage, and the total consumption.[2]