[edarchis]

They're not exactly the same thing but for comparison, France has the Rance Tidal Power Station that has been producing 250MW for 45 years. South Korean made a more powerful one at 254MW. This pilot produced 4.5MW when all 3 turbines were operating normally.

[closewith]

Rance and Sihwa Lake are different beasts as they require sea walls or dams, which are immensely more expensive and environmentally damaging, and have extremely limited suitable sites worldwide. They would never be built now (Sihwa is only 15 years old, but the seawall was built in 1994). They are essentially low head hydro installations fed by the tidal range.

The installation in the Pentland Firth is a fundamentally different category as it is installed in open water (albeit in a firth or channel) which is much less environmentally impactful and has 2-4 orders of magnitude more suitable sites globally.

[dominicrose]

This project is interesting but all comparisons are fair with the end in mind, which is the cost per MWh or per "home" over its life. If you need 55 of those to produce 250MW you'll have to multiply the costs by 55 as well. Power also has to be available all the time, when there is no sun, no wind, no waves, etc. Nuclear and gasoline are sadly the top picks because of energy density (and in the case of gasoline also portability).