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Ocean Energy

Fast Facts About
Ocean Energy

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Principal Energy Use: Electricity
Forms of Energy: Motion/Thermal

Ocean energy, also known as marine energy or hydrokinetic energy, is an abundant renewable energy resource that uses ocean water to generate electricity. The majority of ocean energy technologies are still in research and development. While the potential of ocean energy is vast, it faces significant technological, environmental, and financial challenges and has low levels of investment.

There are four main types of ocean energy systems:

  1. Tidal Barrage Systems are dam-like structures built across ocean inlets to form a tidal basin. Installed turbines inside the tidal barrage let water in to fill up the basin during times of high tide, and let the water flow out during times of low tide, generating electricity in both directions.
  2. Tidal Stream (or Tidal Current) Systems use electrical generators installed directly into the stream of water, similar to placing wind turbines underwater. As water flows through the generators, they harness kinetic energy of the water and convert it into electricity.
  3. Wave Energy Systems use the motion of waves to run a system that converts the mechanical energy of wave motion into electrical energy.
  4. Ocean Thermal Energy Conversion (OTEC) takes advantage of the temperature difference between warm surface water and much colder water at depth to power a turbine in a closed-loop system that can generate electricity

The statistics in this Fast Facts only include data for countries that participate in the Ocean Energy Systems (OES) organization under the IEA. Here is a complete list of member countries.

Significance

Energy Mix

<0.01% of world 🌎
0% of U.S.* 🇺🇸

Electricity Generation

<0.02% of world 🌎
0% of U.S.* 🇺🇸

Change in Global Ocean Energy Installed Capacity

Decrease:
⬇ 4%
(2019-2024)

*The U.S. does not have any commercial ocean energy capacity.

World

Capacity of Largest Operational Ocean Energy Projects

Sihwa Lake Tidal Barrage (Korea)
254 MW

La Rance Tidal Barrage (France)
240 MW

The two tidal barrage plants represent 96% of the 513 MW of 2024 installed capacity.

Drivers

  • Abundant, renewable energy source
  • No air or greenhouse gas emissions
  • Water is 830x more dense than air, so smaller ocean energy systems are able to capture the same amount of energy as larger wind turbines
  • Tidal energy is predictable
  • Many large cities (high demand centers) are coastal
  • Local renewable resource for islands
  • Potential to produce fresh water through OTEC open cycle technologies
  • Public and private investment is increasing, but from a very small base

Barriers

  • Local opposition (NIMBY/BANANA*)
  • Site-specific resource
  • Harsh environment (salt water, biofouling, storms) can corrode materials and slash useful lifetime of energy systems
  • Wave energy depends on weather patterns
  • Most technologies remain in pilot stages (tidal stream and wave energy are beginning commercial deployment)
  • Not cost-competitive with other renewable energy sources like solar, wind, hydro
  • Inconsistent policy support and low investment relative to other renewable energy sources
  • Environmental concerns (marine life)
  • Competing uses (recreation, fishing, marine navigation)

*NIMBY - not in my backyard; BANANA - build absolutely nothing anywhere near anything

Climate Impact: Low

Low gradient
  • Near zero emissions

Environmental Impact: Medium

medium on a scale from low to high
  • No air pollution, but potential for significant impact to marine species and their habitats
  • Collision of marine life with underwater turbines
  • Creation of underwater noise pollution
  • Habitat changes
Sources
 

Updated January 2026

Our 10-Minute Take On
Ocean Energy

If you're short on time, start by watching this video of key highlights from our lecture on Ocean Energy.

Diana Gragg

Presented by: Diana Gragg, PhD; Core Lecturer, Civil and Environmental Engineering, Stanford University; Explore Energy Managing Director, Precourt Institute for Energy
 

Recorded: August 15, 2025  
Duration: 10 minutes

Slides available upon request.

If you liked this video, watch the other 10-Minute Takes here!

Before You Watch Our Lecture on
Ocean Energy

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential videos and readings before watching our lecture on Ocean Energy. Include selections from the Optional and Useful list based on your interests and available time. 

Essential

Optional and Useful

  • Tidal Power 101. Student Energy. May 17, 2015. (2 min)
    Simple description of how tides are formed and how different tidal energy technologies work.
  • Can Underwater Turbines Solve Our Energy Problems?. Real Engineering. Dec 7, 2019. (14 min)
    Great description of tidal energy, including details on the two largest barrage tidal power plants and the status of today’s tidal stream efforts, especially in Scotland.
  • Cheap, Renewable, Clean Energy. There's Just One Problem. Tom Scott. November 28, 2022. (5 min)
    Tidal energy potential and challenges in the Bay of Fundy, the location of the largest tides in the world.
  • How Waves Could Power A Clean Energy Future. CNBC. September 3, 2022. (15 min)
    Video describes the technologies used by the three main wave energy players in the United States and the federal programs that support wave energy research.

Our Lecture on
Ocean Energy

This is our Stanford University Understand Energy course lecture on ocean energy. We strongly encourage you to watch the full lecture to understand ocean energy's role in our energy system. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Diana Gragg

Presented by: Diana Gragg, PhD; Core Lecturer, Civil and Environmental Engineering, Stanford University; Explore Energy Managing Director, Precourt Institute for Energy
Recorded on: May 28, 2025   Duration: 31 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Introduction 
05:41 Potential, History, and Environment 
08:08 Flowing Kinetic: Tidal Energy and Ocean Currents 
19:14 Oscillating Kinetic: Wave Energy 
25:08 Thermal: OTEC (Ocean Thermal Energy Conversion) 
29:10 Chemical: Salinity Gradient 
30:02 Future of Ocean Energy

Lecture slides available upon request.

Additional Resources About
Ocean Energy

Stanford University

Government and International Organizations

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Fast Facts Sources

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