Four units of energy input produce three units of output which is low cost, highly valued hydraulic and electrical energy. Most small dam facilities have a long life and do not require much maintenance. They require few personnel to operate and most are operated completely by remote control. In comparison to large dams, small dams cannot hold as much water, causing there to be less force on the water. There is also a lesser amount of generators that can be used to create electricity.
Larger dams can hold more water and can use more generators.
However, they require much more land use. Low head generators must be placed where there is water flow. They need to be protected properly so that debris does not clog or obstruct the generator. Also, water needs to be channeled into it, so the current going through it is stronger and produces more energy. Generators use no fuel and maintenance is minimal.