Wave energy converters: Efficiency
Why nobody agrees how efficient a wave machine is
What this tab covers How much of the energy available is actually captured or extracted, in per cent: theoretical limits, laboratory records, typical new equipment and in-service averages, each with exactly what is being measured.Wave devices are judged by how much of the wave power arriving across their width they absorb (hydrodynamic efficiency), then by how well the power take-off turns that into electricity. Tested values spread widely, from a few per cent to over 50%, and real plants run at low load factors.
Chart: Efficiency ranges
Record In service CommercialEfficiency by measure
| Measure | Range | Type | What is measured |
|---|---|---|---|
| Oscillating water columns | 2 to 71%1 | Record | Hydrodynamic or pneumatic efficiency in tests and models (71% is a lab peak at resonance); the full-scale Pico sea trial gave 20% pneumatic |
| Heaving point absorbers (buoys) | 3 to 51%1 | Record | Hydrodynamic efficiency, tests and models; best results from the Wavebob design |
| Pitching attenuator (Pelamis) | 14 to 21%1 | In service | Hydrodynamic efficiency at different sites |
| Overtopping (Wave Dragon) | 18 to 27%1 | In service | Hydrodynamic efficiency, sea trial and simulation |
| Surge flaps (Oyster-type), tank tests | 35 to 65%1 | Record | Hydrodynamic efficiency in a wave tank |
| Power take-off | 55 to 95%1 | Commercial | Mechanical or pneumatic power to electricity: air turbine 55%, hydraulic 65%, direct-drive linear generator 95% |
| Mutriku OWC breakwater, 2024 | 8%23 | In service | Capacity factor: 210 MWh from 296 kW (calculated) |
Where the energy is lost
| Step | Loss |
|---|---|
| Waves passing, reflecting or out of tune with the device | most of the incident power for many designs1 |
| Air turbine in an oscillating water column | about 40-50% of pneumatic power (calculated from 50-60% turbine efficiency)2 |
| Downtime for repairs | availability 70-80% in 2010-2012 estimates2 |
There is no single theoretical limit like the Betz limit for wind, because absorption depends on device shape and tuning to the wave period. A floating body can absorb power from a crest wider than itself, which is why a few lab results look high. Comparing devices is hard: reviewers note that efficiencies are measured at different stages (pneumatic, mechanical, electrical) and under different wave climates.
Sources
- Review on Power Performance and Efficiency of Wave Energy Converters (Aderinto and Li, Energies 12, 4329), Tables 3-8 MDPI (copy hosted by PNNL Tethys), 2019
- Wave Energy: Technology Brief IRENA, 2014
- Ocean Energy: Key Trends and Statistics 2024 Ocean Energy Europe (copy hosted by PNNL Tethys), 2025