What is the difference between small-scale and large-scale hydropower projects?

Small-scale hydropower is usually 10 MW or less in size. One of the common definitions for micro hydropower is a rated capacity of 300 kW or less. The 300 kW limit is because this is about the maximum size for most stand alone hydro systems not connected to the grid, and suitable for "run-of-the-river" installations. Small-scale hydro is normally run of the river design and is one of the most environmentally benign energy conversion options available, because it does not attempt to interfere significantly with river flows. The break point between small-scale and large-scale hydro differs from country to country ranging between 10 and 50 megawatts (MW).