Looks like the first tidal power plant was built in 1966 in Brittany: https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station https://en.wikipedia.org/wiki/Ranc

Looks like the first tidal power plant was built in 1966 in Brittany: https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station. It was also the largest for 45 years until a bigger one opened in South Korea: https://en.wikipedia.org/wiki/Sihwa_Lake_Tidal_Power_Station https://en.wikipedia.org/wiki/Sihwa_Lake_Tidal_Power_Station. Not sure if someone has an analysis about why those aren't more widespread ? It seems like the existing ones are pretty massive and in very specific spots, maybe smaller installations aren't cost-effective enough.