Hydroelectric Dam vs Run Of River vs Pumped Storage Hydro Energy: Comparison

There are several different types of hydro energy setups used to generate electricity globally.

In the guide below, we compare hydroelectric dams vs run of river vs pumped storage hydro energy setups.

We look at what each is, their differences, and examples of each being used in the world.


Summary – Hydroelectric Dam vs Run Of River vs Pumped Storage Hydro Energy

Firstly, What Is Hydro Energy?

Hydro energy is the use of the mechanical energy from water (usually from freshwater bodies) to create electricity


Main Types Of Hydro Energy

The main types of hydro energy are:

– Hydroelectric Dams (also called an ‘Impoundment Facility’)

– Run Of River (also called ‘Diversion’)

– Pumped Storage Hydro


Below, we outline what each of these types of hydro energy are, and we also outline potential differences between them.


Different Sizes Of Hydro Projects

Hydro projects can also be categorised by their size, with size being their electricity generation capacity.

Those size categories might be:

– Large

– Medium

– Small (and micro sized)


Some of the largest hydro projects in the world are hydroelectric dams.

Below, we give the general electricity generation capacity ranges for the different types of hydro setups, and identify where some of the largest hydro projects in the world are located.


What Are Hydroelectric Dams (Impoundment Facilities), & How Do They Work?

What Are Hydroelectric Dams?

Hydroelectric dams are power plants that are usually built on rivers

The involve an impoundment facility that contains a dam that holds a reservoir of water

Hydroelectric dams are some of the largest capacity hydro energy power plants, and are one of the largest producers of electricity 


How Do Hydroelectric Dams Work?

The way they work is relatively simple:

– A man-made dam holds/stores water in a reservoir

– Water is released from the reservoir, and it spins a turbine that is connected to a generator

– The turbine generates electricity


The volume of water, and the height of the water above the turbine, can both impact how much electricity is generated.


Other Potential Benefits Of Hydroelectric Dams

Other than electricity generation, hydro electric dams can also play a role in the prevention of flooding, along with providing other functions.


What Is Run Of River (Diversion), & How Does It Work?

What Is Run Of River?

Run of river hydroelectricity plants use a flowing water source (such as a stream or river) to generate electricity

Instead of using a storage area or reservoir like an impoundment facility, a run of river setup diverts a % of flowing water for electricity generation

Run of river setups may or may not still use some type of small dam, depending on the setup


How Does Run Of River Work?

– A % of water from the running/flowing river or stream is diverted through an intake that is angled off from the river/stream

– The water flows through a channel or penstock, and is channeled to a turbine

– The turbine is connected to a generator which generates electricity

– Most of the water might be returned to the river/stream downstream


Factors That May Impact Run Of River

Run of river may be impacted by whether the river flow is consistent or not throughout the seasons, or, throughout the year

Where a river is seasonal with it’s flow, power delivery can be variable/intermittent

Where a river is flowing year-round, and/or has storage capability (known as pondage), power delivery might be more consistent


What Is Pumped Storage Hydro Energy, & How Does It Work?

What Is Pumped Storage Hydro?

Pumped storage hydro uses two water reservoirs – one lower, and one higher level reservoir – to generate electricity


How Does Pumped Storage Hydro Work?

– Water is stored in a lower level water reservoir 

– Water is pumped to an upper level/higher level water reservoir (up hill, or up an elevation)

– When there is a demand for electricity, water is released from the higher level water reservoir to the lower one, and on the way, the water flows through a turbine that is connected to a generator, generating electricity


Fossil fuels might be used as a fuel source to pump water from the lower level to the higher level reservoir. Although, some renewable energy sources like solar might be used as a % of energy for pumping water with this setup in the future.

Pumped storage hydro may also be able to be used to store surplus renewable energy by pumping water to the higher reservoir when there’s surplus renewable energy, and releasing the water back down when there’s a renewable energy deficit.


Other Notes On Pumped Storage Hydro

We provide some other notes on pumped storage hydro in a separate guide.


Hydroelectric Dam vs Run Of River vs Pumped Storage Hydro: Main Differences

Some of the potential differences between the different types of hydro energy setups might be:

– Use Of Storage Areas & Reservoirs

Hydroelectric dams use a reservoir, and pumped storage hydro uses two reservoirs

Run of river doesn’t typically use a reservoir, but, may sometimes use pondage


– Use Of Dams, & Use Of Rivers & Streams

Hydroelectric dams obviously have a dam as a centrepiece of how they function

Run of river may sometimes use a small dam, but doesn’t always

Both of these hydro energy setups are built across or offside a river or stream 

Pumped storage hydro doesn’t use a dam, and isn’t built on or alongside a river or stream


– Variability/Intermittency

Run of river setups that don’t use pondage or small dams will be variable/intermittent if water flow is seasonal

Hydroelectric dams with large storage capacity and pumped storage hydro with large capacity may be more consistent as long as there is water available to use and release through turbines


– Ability To ‘Ramp Up’

Hydroelectric dams and pumped storage hydro may typically be able to ‘ramp up’ more quickly to meet peak demand compared to run of river setups that don’t use pondage or that don’t have small dams, because they store water that can be released at a suitable time


– Environmental Impact

Some reports indicate that large hydroelectric dams may have a more negative impact on the environment (the surrounding aquatic environment, and aquatic life), compared to other types of hydro setups such as run of river setups that simply divert water through a canal/penstock

Having said that, pumped hydro may require land clearing, and may also use fossil fuels to pump water to the higher reservoir


– Practical Benefits

Pumped storage hydro may be more flexible than the other two types of hydro energy setups – being able to pump and release water almost at will. This may make pumped storage hydro suitable as a baseload energy source that can complement the intermittent nature of solar or wind 

Pumped storage hydro may also be able to store ‘surplus’ renewable energy by using this surplus energy to pump water, and then releasing this water when renewable energy goes into supply/demand deficit.


– Other Factors That Can Differ Between Projects

Cost, capacity, and efficiency can all differ between different hydro energy projects

The largest capacity projects (with the largest power outputs) are usually the most expensive – large hydroelectric dams have traditionally been as example of this

We provide more information on power capacity below


Small vs Large Capacity Hydro Energy Projects (Different Sized Hydro Projects)

Hydro energy projects come in different sizes, with size being a reference to the electricity generation capacity of the project or power plant.


Small, Medium, & Large Hydro Setups

– Micro & Small Hydro

Might be used by individuals, or small communities.

May involve hydro water wheels or similar devices that utilise hydro energy.


– Medium Hydro

Generally used for utility scale electricity generation


– Large Hydro

Hydro setups used for utility scale electricity generation. 

The largest hydro projects tend to be hydroelectric dams (which produce the most electricity)

The Three Gorges Dam for example produces up to 22,500 MW – one of the largest energy generation capacities in the world.


sciencealert.com also notes how some of the largest pumped storage hydro energy setups may have a large capacity in the future

sciencealert.com notes that:

New potential pumped storage sites discovered in recent studies have potential capacity to hold 2-150 GWh of energy


2 GWh might convert to roughly 2000 MWh


Potential Power Capacity Ranges & Categories

There’s no ‘official’ sizing definitions (in terms of electricity generation capacity) for the different sized hydro projects.


However, wikipedia.org gives a guideline on what hydro project size ranges and categories might look like: 

Large – 10 GW (10,000 MW) and over

Small – 10-30 megawatts (MW)

Micro and Pico – in the kW range


Electricity Generation Capacity Of The Different Types Of Hydro Setups

Right now, hydroelectric dams may have the highest max capacity

This is followed by run of river, and then pumped storage hydro


– Hydroelectric Dams

[Hydroelectric dams can range …] from 1000 all the way up to 22,500 MW of capacity (wikipedia.org)


– Run Of River

From wikipedia.org:

[There might be high] variance in capacity of the major examples of run of river hydro plants globally.

[They range …] from 16MW of capacity … all the way up to 11,233 megawatts of capacity …


– Pumped Storage Hydro

[Pumped storage hydro sites range] between 1000 to 3000MW of capacity (wikipedia.org)


Countries With The Largest Hydro Projects

Hydroelectric Dams

Paraphrased from wikipedia.org, China has some of the largest hydroelectric dams in the world

The Three Gorges Dam (on the Yangtze River) is an example


Run Of River

[The] Belo Monte Dam in Brazil [has] 11,233 megawatts of capacity … (wikipedia.org)


Pumped Storage Hydro

China, the US, Japan, Australia, Spain and France has some of the [pumped storage hydro sites] with the largest capacity (wikipedia.org)




1. https://www.irena.org/hydropower

2. https://www.energy.gov/eere/water/types-hydropower-plants

3. https://en.wikipedia.org/wiki/Hydroelectricity

4. https://www.vox.com/energy-and-environment/2019/6/18/18681591/renewable-energy-china-solar-pv-jobs

5. Various ‘Better Meets Reality’ guides

6. https://www.iea.org/renewables2018/power/

7. https://www.iea.org/newsroom/news/2018/october/modern-bioenergy-leads-the-growth-of-all-renewables-to-2023-according-to-latest-.html

8. https://en.wikipedia.org/wiki/List_of_conventional_hydroelectric_power_stations

9. https://en.wikipedia.org/wiki/Run-of-the-river_hydroelectricity

10. https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroelectric_power_stations

11. https://www.sciencealert.com/scientists-spot-530-000-potential-pumped-hydro-sites-to-meet-all-our-renewable-energy-needs

12. https://www.cnet.com/news/if-renewable-energy-can-power-entire-countries-why-isnt-everyone-doing-it/

13. https://www.abc.net.au/news/2017-02-03/pumped-hydro-and-its-potential-in-sa-explained/8233342

14. https://www.worldenergy.org/data/resources/resource/hydropower/

15. http://www.wvic.com/content/facts_about_hydropower.cfm

16. https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

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