Hydropower is the generation of electricity by harnessing the power of moving water using a water turbine. Large-scale hydro generates around 20% of the world's electricity supply. However, on a small scale, hydropower can be a very efficient way of generating electricity.

The energy in the water can be transformed into electricity whenever water passes from a high level to a lower one, for example at a waterfall or a man-made weir. With small hydro systems, a dam or barrage across the whole river is not always necessary. A small section of the river can be diverted, which results in minimising the effect on the environment. A suitable site for a mini-hydro installation will require a good year-round water supply, access to and permission to build on the land surrounding the location and an end user close to the site (simply feeding into the grid will not be economically viable for smaller installations). The necessary environmental studies will also have to be undertaken.

Hydropower is a reliable, efficient form of electricity generation. Variations in output may vary seasonally or daily, according to rainfall but in general, this method of generation gives a very predictable output.

The water flow rate cannot vary too much throughout the year. A licence must be obtained after a full environmental assessment of the site has taken place, which can be a time consuming process. It is preferred if the end-user of the electricity source is located close to the turbine. A minimum potential of a 5kW installation is required for a site to be economically viable.

For smaller sites (5-10kW), the cost will be around £2000/kW installed. Larger sites (10-20kW) will cost around £1000/kW.

Please email or call CEN on 020 8683 6694 for further information or advice.