Tidal energy cost per kWh, compared
Tidal stream is more expensive per unit than offshore wind or solar today, and clearly so. Any single figure quoted without a date and a discount rate should be treated with suspicion, because those two assumptions move it more than the technology does.
Where tidal sits
| Source | Relative cost per unit | Why |
|---|---|---|
| Solar / onshore wind | lowest | Mass produced, mature supply chain |
| Offshore wind | low to moderate | Now mature after two decades of scale |
| Nuclear | moderate to high | High capital, very long life |
| *Tidal stream | high today | Bespoke projects, expensive sea access, no volume yet |
| Tidal barrage | high upfront, low over a long life | Civil structure lasts generations |
Read the ranking, not a number
The order here is stable. A precise cost per kWh is not, because it depends on the size of the project, the cost of money and the assumed lifetime, each of which can move the figure by more than the choice of technology.
Why the figures move so much
Three things dominate any quoted number: project size, because a single demonstrator carries all its fixed costs alone; the discount rate, because capital heavy and fuel free generation is extremely sensitive to the cost of money; and the assumed life, because spreading capital over 25 years rather than 15 changes the per unit figure substantially.
What a per unit comparison hides
Cost per kWh treats every kWh as equal, and a grid does not. Power that can be scheduled years ahead displaces reserve that would otherwise be paid for, and power that arrives at a known time is worth more than the same energy at random. That is the core of the tidal argument, and it does not show up in a simple price. See is tidal energy expensive for the short version.