Hydropower dams: Techniques

Francis, Kaplan or Pelton: matching the turbine to the drop

What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.

A storage dam holds back a river to create a reservoir and a height difference, then releases water through turbines when power is needed. The three main turbine types suit different heads.

Comparison

Method	Efficiency	Cost	Life-cycle emissions	Maturity	Scale
Storage dams with Francis, Kaplan and Pelton turbines¹²³⁴⁵⁶¹⁵¹⁶	Over 90% at the turbine; 43% average capacity factor for 2025 projects	USD 62/MWh global average LCOE for 2025 projects, installed cost USD 2,079/kW (IRENA, 2025 USD); large projects USD 1,050-7,650/kW (IRENA 2012, 2010 USD)	Median 24 g CO2e/kWh, but range 1-2,200 (IPCC AR5); 6-147 g CO2e/kWh depending on site (UNECE 2022). Emissions come mainly from methane released by decaying organic matter in reservoirs, especially in warm climates.	mature	1,469 GW of hydropower worldwide at end of 2025 including 201 GW of pumped storage, so about 1,268 GW conventional (calculated); about 16 GW of conventional capacity added in 2025 (calculated from 28 GW total minus 11.7 GW pumped storage); about 4,500 TWh generated a year (IHA)

Hydropower was the cheapest renewable source in 2010 (about USD 44/MWh, calculated from the 41% rise IRENA reports), but its average cost rose to USD 62/MWh in 2025 (IRENA). Installed costs rose from USD 1,494/kW in 2010 to USD 2,267/kW in 2024 (2024, IRENA); plants commissioned in 2025 averaged USD 2,079/kW. Because about three-quarters of investment is site-specific civil works, costs depend heavily on which sites are being built. New onshore wind, at USD 33/MWh on average, is now cheaper. Hydropower's value lies in being dispatchable: a reservoir is a large store of energy that can follow demand and balance wind and solar. Its emissions vary more than any other renewable source, from near zero for cold, deep reservoirs to levels comparable with fossil plants for shallow tropical ones.

How each method works

Storage dams with Francis, Kaplan and Pelton turbines

A dam of concrete, earth or rock raises the water level and stores months of river flow. Water runs down a penstock (a large pipe) to the powerhouse. In Francis and Kaplan (reaction) turbines, water fills the runner and pushes on curved blades as it flows through; in Pelton (impulse) turbines, jets strike buckets on a wheel. The shaft drives a generator, and gates control the flow, so output can be ramped up or down within minutes.¹²³⁴⁵⁶¹⁵¹⁶

Sources

Hydropower: Technology Brief E06 (Table 2, turbine efficiency) IRENA and IEA-ETSAP, 2015
Renewable Power Generation Costs in 2025 (Executive summary, Figure S1) IRENA, 2026
Renewable Energy Technologies: Cost Analysis Series, Hydropower (Volume 1, Issue 3/5) IRENA, 2012
Climate Change 2014: Mitigation, Annex III Technology-specific cost and performance parameters, Table A.III.2 (life-cycle emissions, min/median/max) IPCC AR5 Working Group III, 2014
Carbon neutrality in the UNECE region: integrated life-cycle assessment of electricity sources (ECE/ENERGY/141) United Nations Economic Commission for Europe, 2022
Year of the water battery: global pumped storage capacity surpasses 200 GW (2026 World Hydropower Outlook) International Hydropower Association, 2026
Hydropower technologies (Waheed et al., in Renewable Energy Technologies, pp. 591-632) Elsevier, 2025
Renewable Power Generation Costs in 2024: Summary (Table S1) IRENA, 2025