A Net Zero Energy Building is one that consumes as much energy as it produces. This is accomplished by adopting renewable sources of energy. Renewable sources include wind, solar, hydro, geothermal, and biomass. During peak demand times, a net zero energy building will draw from the local grid as needed. When energy production exceeds consumption, the surplus is sent back to the grid for storage or it's stored on site to be used later. Buildings can be considered energy autonomous when they are able to produce and store enough energy on site to meet the energy demands of the building without drawing from the grid. Renewable energy adoption in conjunction with energy conservation best practices allows many buildings to become net zero energy buildings.