How water power works
Water (or hydro) power systems use the potential energy stored in water to turn a turbine and produce electricity.
Power can be produced from even a small stream, and a micro (small) hydro plant is one that is sized less than 100 kilowatts (kW).
The Energy Saving Trust says that improvements in small turbine and generator technology mean that small hydro schemes are an attractive means of producing electricity.
Hydro systems can be connected to the national electricity grid or be part of a stand-alone (off-grid) power system. In a grid-connected system, any electricity generated, but not used, can be sold to electricity companies.
In an off-grid hydro system, electricity can be supplied directly to the devices powered or through a battery. A back-up power system may be needed to compensate for changes in water flow throughout the year.
Installing a water power system
Water power requires the water source to be relatively close to where you will use the electricity generated, or to a suitable grid connection.
The amount of energy generated depends on how fast the water flows and how far the water falls. In small systems, around half of the power of the water is actually converted to electrical power.
You will need to talk to your local authority’s planning team to ensure the site and design are acceptable. You will also need to check if you need any other permissions.
The cost of water power
Water power costs depend on the site and energy output. For small systems using an existing pond or weir, costs could be in the region of £4,000 per kW installed up to about 10kW. The costs per kW would drop for larger schemes.
For medium sized systems, there is a fixed cost of about £10,000 and then about £2,500 per kW up to around 10kW. A typical 5kW domestic scheme might cost £20,000 to £25,000, according to the Energy Saving Trust. The cost will vary depending on location.
How water power can save you money
Producing your own energy could be cheaper than buying it from energy companies. In addition, you can also sell any excess energy you generate to energy companies, using Feed-in Tariffs (FITs).
The FITs scheme guarantees a minimum payment for all electricity you generate, as well paying you for any electricity you export to the national grid. The Energy Saving Trust’s website has more information about FITs.