An important advantage of hydroelectric dams is their ability to be used as a peaking power plant. When the electricity demand declines, the dam simply stores more water. Water that has been stored in a reservoir can be released (let go) when needed, so the energy can be made quickly. Some hydroelectricity generators use pumped storage to store excess energy (often during the night), by using the electricity to pump water up into a basin. Electricity can be generated when demand increases. This flexibility also makes hydroelectricity a good match for less controllable intermittent energy sources. When the wind is not blowing or the sun is not shining, hydroelectricity can be created.