Tidal stream energy is electricity produced by turbines placed in fast tidal currents, usually on the seabed or hanging from floating platforms. The rotors work much like wind turbines, but water is far denser than air, so slower currents can still drive them. It is different from tidal range power, such as a barrage or lagoon, which holds water behind a wall and releases it through turbines.
Why it interests grid planners
Tides follow the moon, so output can be forecast years ahead, unlike wind or sunshine. Output still rises and falls through each tidal cycle, with four slack periods a day, so it is predictable rather than constant.
UK status
- Operating capacity: DESNZ puts UK wave and tidal stream capacity at 9.8 MW in 2025, generating about 16 GWh, from three generating stations.
- MeyGen: a seabed turbine array in the Inner Sound of the Pentland Firth, off Caithness, and the largest tidal stream site in the UK.
- Orbital O2: a floating turbine with two rotors at the European Marine Energy Centre in Orkney. Orbital Marine Power says it is rated at 2 MW and has exported to the grid since 2021.
Contracts for Difference
The government ring-fenced part of the Contracts for Difference budget for tidal stream in allocation rounds 4, 5 and 6. In round 7a, results of which were published in February 2026, there was no ring-fence and tidal stream competed in Pot 2.
| Round | Tidal stream capacity awarded |
|---|---|
| AR4 | 40.82 MW |
| AR5 | 53.04 MW |
| AR6 | 28 MW |
| AR7a | 20.9 MW at £265/MWh (2024 prices) |
ORE Catapult puts total contracted tidal stream capacity at just over 140 MW across three sites, most of it due to be commissioned in 2027 and 2028. MeyGen won 28 MW, 21.94 MW and 9 MW in rounds 4 to 6.
Read more: Wave and tidal energy: how marine power works and where the UK stands.