**Hydropower** systems can be engineered to work efficiently in a variety of water environments.

There are many different types of hydropower turbine generators, and their sizes and locations vary due to many different variables.

The two most important variables are the volume of water available and the height of the vertical drop of the water.

The potential energy of the water measured through the vertical height of the water is called the head. The head is either measured by distance (feet) or by pressure (pounds per square inch).

The flow or volume of water is the amount of water that passes through the hydropower turbine in a given unit of time. When the flow and the head are calculated together we get the potential of the water power expressed in watts for that specific type of hydropower system.

We can actually get the same proportional hydropower output in watts from water that is high in volume with a small head height versus water that is low in volume with a large head height. These two varieties of water conditions result in the two main types if hydroelectric power turbines that we find today.

We use small hydropower generators for low volume & high head water systems, and much larger hydropower turbine generators for a high volume & low head system.

Besides the size of the turbines, most of the working components in the different types of hydroelectric systems function in similar ways.

The **biggest difference** between the two types of hydropower systems (a high head and a low head turbine generator) is that a low head system requires a much larger generator to account for the higher volume and flow of water needed. Any two systems could potentially create the same amount of electric power as long as certain adjustments are made to the size of the turbine and the volume of flowing water.

So, because of this important difference between the two main types of hydropower systems, the cost of each will vary greatly. The cost of a larger turbine, which would require significantly more material and resources, will usually be the more expensive of the two. However, either type of hydropower system can be an affordable approach to using renewable water energy to generate electricity.