Can Wave & Tidal Power be Part of the Energy Transition?

Making use of the moon to power everything from hairdryers to cars sounds like a sci-fi concept, but humans have been harnessing the tides for a very long time. In the first century AD, Romans used tidal mills to grind grain and, with the energy transition underway, this renewable power source could make a comeback.

Tides can be predicted with a high degree of accuracy far into the future, even centuries ahead. These predictions are based on the well-understood gravitational interactions between the Earth, Moon and Sun. While influenced by the wind, waves have inertia and maintain energy over time, making them more reliable than wind and sun forecasts used for solar and wind power. 

Wave and tidal energy technologies are still immature and involve bespoke, highly engineered systems that must withstand harsh marine environments. Corrosive saltwater and strong tides contribute to making costs for this power significantly higher than other renewable sources. The Offshore Renewable Energy Catapult, part of the UK's national innovation agency, says that tidal energy costs could fall 80% by 2035 with the right technological developments.

Read the full story in the August 2025 edition of Sustainability Magazine.

La Rance Tidal Power Station

Despite being a relatively new introduction to the energy transition so far, tidal power stations do exist and are successfully generating electricity around the world. 

On the estuary of the Rance River in Brittany, France, sits one of the biggest, and oldest, tidal power projects in the world. The Rance Estuary has one of the world’s highest tidal ranges at 13.5 metres. Ideas for the “Usine marémotrice de la Rance” were born in the 19th Century, but work did not begin on the project until 1943.

La Rance Tidal Power Station began generating electricity in 1966 and today, the plant accounts for 40% of the electricity generated in the Brittany region – around 500 GWh per year. The development of “bulb” generators began specifically for this plant, and they are now used all over the world. In total, its development cost 620 million francs (around US$7bn in 2025).

More recently, EDF has invested €100m (US$112.3m) between 2015 and 2025 to renovate the 24 bulb turbines, gates and automatic control systems alongside replacing the extra high voltage outgoing transmission cables. The facility has a capacity of 240 MW.

While the project’s costs have been significant over its lifetime, it has produced roughly 27,600 GWh of electricity since its construction – worth roughly US$7.7bn using 2025 energy costs in France.

Wave and tidal projects around the world

La Rance was the biggest tidal energy project in the world until 2011 when K-Water’s Sihwa Lake Tidal Power Plant took the top spot with a capacity of 254 MW. 

The Sihwa Lake Tidal Power Plant makes use of a seawall that was constructed in 1994 for flood mitigation. It uses 10 bulb turbines and generates power on tidal inflows with a mean operating tidal range of 5.6 metres. Construction on the project began in 2011 and it began operations in 2012 at a cost of US$650m. The original seawall was built in part due to water pollution, but the lake’s quality deteriorated due to limited natural inflows. To address this, the plant now circulates around 145 million tonnes of seawater in and out of the lake. A 75 metre high observatory has made the facility a popular tourist destination, with more than 1.4 million visitors each year.

Located off the coast of Scotland, MeyGen has been in operation since March 2018 and has delivered more than 51 GWh of renewable electricity. “The project will be transformational for the tidal energy industry, delivering the world's first commercial scale tidal array and securing MeyGen as the home of tidal energy,” SAE Renewables’ website says. The project’s second phase has been awarded a Contract for Difference for 59 MW and a lease from the Crown Estate allows for up to 398 MW of capacity.

The PowerBuoy, OPT’s flagship product, is deployed internationally including across the US, UK, Spain and Australia. Its wave parks in the US in Oregon and New Jersey, along with the PowerBuoy Mark 3 and Hybrid PowerBuoy, have demonstrated technical reliability in harsh ocean environments. OPT’s grid-connected solutions serve both civilian and defence applications, looking to support commercialisation of wave energy.

The Morlais Tidal Power Station in Wales is set to offer a “plug and play” approach to tidal energy developers, helping to reduce costs as operations scale up. The site has the potential to generate enough energy to power 180,000 typical Welsh households. Construction on the project began in 2022 with elements like an onshore substation already completed. 

Orbital Marine Power has pioneered “floating” tidal turbines with its O2 machine, described as the world’s most powerful operational tidal device. Based in Orkney, Scotland, Orbital plans to expand to a 30 MW Westray Firth project and apply its modular technology globally. The business sees tidal stream as a key pillar for decarbonised energy systems, with multi-turbine arrays on the horizon and projects planned for both UK and US waters.

Does marine energy have a place in the transition?

The International Renewable Energy Agency estimates that 90% of the world's electricity can, and should, come from renewable energy by 2050. Energy companies have integrated this into their strategies, often aiming to significantly boost renewables.

NextEra Energy aims to reach 81 GW of renewables and energy storage capacity by 2027. In its 2024 sustainability report, John Ketchum, the company’s President and CEO, said: “Today, our vision is focused on deploying even more renewables and storage, which in the future we expect to be supplemented by green hydrogen as a way to convert gas turbines to generate emissions-free baseload generation.”

Iberdrola is targeting 95 GW of installed renewables by 2030. "We need to accelerate the expansion of electrification through renewables to reduce our dependence on fossil fuels,” says Ignacio Galán, President of Iberdrola. “Tripling renewables by 2030 is feasible and will mobilise investments of US$2.2bn a year.” 

Marine energy, however, is not yet mentioned in the strategies of many big energy businesses. Pilots are being tested and projects are being built, but both wave and tidal energy have a long way to go before the technologies could play a significant role in the energy transition. In 2025, marine energy costs roughly US$350 per MWh – for comparison, natural gas is around US$36 per MWh and wind is roughly US$50 per MWh in Europe. 

Will marine energy grow?

Despite such high prices currently, progress is possible and has been done before. In 2009, electricity from utility-scale solar photovoltaics cost US$496 per MWh and in 2025 this has dropped to around US$50 per MWh. This is nearly a 90% decrease in price over 16 years. Offshore Renewable Energy Catapult estimates following an optimistic scenario that the price of marine energy could fall to about US$67 per MWh by 2035. This could make it lower than current nuclear energy prices if solutions are successfully commercialised.

Sue Barr, Chair of the UK Marine Energy Council, said: “With over 90 MW of potential tidal energy projects due to deliver projects across Scotland and Wales in coming years, there is a clear signal that tidal technology is moving towards a commercially viable future.

“Our ambitious UK target of 1 GW of installed capacity by 2035 means it is imperative we can define the levers and strategies which can strengthen delivery of tidal stream technology into our energy system.”

Read the full story in the August 2025 edition of Sustainability Magazine.