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Hydroelectricity’s low cost, near-zero emissions, and ability to be dispatched quickly to meet peak electricity demand worldwide.



Hydropower is a renewable, efficient, and reliable source of energy that does not directly emit greenhouse gases or other air pollutants, and that can be scheduled to produce power as needed, depending on water availability. Hydroelectric plants have the advantage of being long-lived and many existing plants have operated for more than 100 years.

Hydropower is also an extremely flexible technology from the perspective of power grid operation. Large hydropower provides one of the lowest cost options in today’s energy market, even compared to fossil fuels and there are no harmful emissions associated with plant operation. Hydroelectric power provides almost one-fifth of the world's electricity. Hydropower is the cheapest way to generate electricity today. That's because once a dam has been built and the equipment installed, the energy source—flowing water—is free. It's a clean fuel source that is renewable yearly by snow and rainfall.

Hydroelectric power is the second major source of low-carbon electricity. Hydro produces only small amounts of CO2 as a byproduct of dam construction and operation, but in some cases may produce significant amounts of another greenhouse gas, methane. The amount of electricity generated by a hydropower facility depends on three factors: 1) the turbine generating capacity; 2) the turbine discharge flow (the volume of water passing through the turbine in a given amount of time), and 3) the site head (the height of the water source or vertical distance between the highest point of water source and the turbine). The higher the head, the more gravitational energy the water has as it passes through the turbine.

Hydropower is a clean source of energy, as it burns no fuel and does not produce greenhouse gas (GHG) emissions, other pollutants, or wastes associated with fossil fuels or nuclear power. However, hydropower does cause indirect GHG emissions, mainly during the construction and flooding of the reservoirs.

Category of the action

Reducing emissions from electric power sector.

What actions do you propose?

  • Development of the following hydropower according to Power output and applicability for producing electricity:


Adapted from SINGH (2009) and GAIUS-OBASEKI (2010)

Hydropower plants are classified according to their energy production capacity, expressed in megawatts. While large scale hydropower plants can produce well over 100 MW, small hydropower plants generally produce less than 10 MW. Based on energy production capacity, small-scale hydropower production is broken into four size categories of pico- (<5 kilowatts), micro- (5-100 kW), mini- 100 kW-1 MW), and small (1-10 MW).

However, classifications vary from country to country as there is currently no common consensus among countries and hydropower associations regarding the upper limit of small-scale hydropower plant capacity. For instance, some European Union countries like Portugal, Spain, Ireland, Greece and Belgium accept 10 MW as the upper limit for small-scale hydropower installed capacity, while others place the maximum capacity from 3 to 1.5 MW. Outside the EU, this limit can be much higher, as in the USA (30 MW) and India (25 MW).

  • Large (> 100 MW): Large urban population centres
  • Medium (10 – 100 MW): Medium urban population centres
  • Small (1 – 10MW): Small communities with possibility to supply electricity to regional grid.
  • Mini (100 kW – 1MW): Small factory or isolated communities.
  • Micro (5 – 100kW): Small isolated communities.
  • Pico (<5kW): 1 – 2 houses.


  • Policy Options to Help Promote Hydropower
  • Price on Carbon

A price on carbon would raise the cost of electricity produced from fossil fuels relative to the cost of electricity from renewable sources, such as hydropower, and other low carbon technologies.

  • Economic Incentives

Different financial incentives (e.g. tax credit bonds, production tax credit, incentive payments are provided to encourage the growth of hydropower generation, improving efficiency at existing projects, and more reliance on renewable electricity sources.

  • Renewable Electricity Standards

Renewable electricity standards (renewable portfolio standards) require electricity providers to gradually increase the amount of renewable energy resources—such as wind, solar, bioenergy, and geothermal—in their electricity supplies, until they reach a specified target by a specified date. The hydropower production growth under these standards is mostly provided through development of small-scale hydropower and this growth is considerably slower than increase in electricity generation from other renewable sources.

Who will take these actions?

The key actors are:

Government, Private sector, Electricity Cooperation, and related organizations.

Where will these actions be taken?


How much will emissions be reduced or sequestered vs. business as usual levels?

Hydropower’s GHG emissions factor 4 to 18 grams CO2 equivalent per kilowatt-hour’ is 36 to 167 times lower than the emissions produced by electricity generation from fossil fuels.

What are other key benefits?

The key benefits are:

· Fuel is not burned so there is minimal pollution

·  Water to run the power plant is provided free by nature

·  Hydropower plays a major role in reducing greenhouse gas emissions

·  Relatively low operations and maintenance costs

·  The technology is reliable and proven over time

·  It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there

What are the proposal’s costs?

Existing hydropower is one of the least expensive sources of power since the cost of hydropower is dominated by the initial capital cost of building the facility while the ongoing operating and maintenance (variable) costs are low. Moreover, since hydropower generation does not require burning fuels, operations costs are not vulnerable to fuel price fluctuations. Existing hydropower facilities are very cheap to operate and they can operate for 50 years or more without major replacement.

A look at the installed project costs – as opposed to levelized electricity costs – for various types and sizes of hydro projects reveals a wide range, and a number of technologies need continued or expanded federal incentives, supportive tax and regulatory environments and other support to improve and deploy at the project level.

  • Conventional Hydro (impoundment) 50MW (average) installed cost $1,000-$5,000: A mature technology, conventional hydro falls at the lower end of the range of installed costs, particularly for upgrade projects at existing sites. New dams and greenfield sites are more expensive.
  • Microhydro < 0.1MW installed cost $4,000-$6,000: The installed cost for low-impact hydro systems is not expected to decline in the near term.
  • Run of River (diversion.) Approx. 10MW installed cost $1,500- $6,000: Similar to conventional hydro, installed costs for run-of-river can vary widely.
  • Pumped Storage >500MW installed costs $1,010-$4,500: Traditional pumped storage is a proven technology and costs are not expected to decline going forward. The new underground pumped storage technology has been quoted at $2,000/kW and cost declines can be expected going forward, if the concept proves itself.

Time line

The four phases of a major hydropower project:

  • Planning: 1-2 years-Preliminary studies
  • Draft design and government permitting: 2 to 5 years-Environmental review (Impact assessment study, Screening analysis, public hearing and decision
  • Construction: 2 to 12 years-Environmental monitoring
  • Operation: 100+ years – Environmental follow up

Related proposals


GAIUS-OBASEKI, T. (2010): Hydropower Opportunities in Water Industry. In: International Journal of Environmental Sciences 1, 392-402.

International Energy Agency (2007). Renewables in global energy supply: An IEA facts sheet

SINGH, D. (2009): Micro Hydro Power Resource Assessment Handbook. New Delhi, India: Renewable Energy Cooperation- Network for the Asia Pacific (RECAP).