The UK is underestimating the amount of electricity that could be generated from tidal sources, new research says.
The analysis says that estuary barrages and tidal streams could provide more than 20% of the nation's demand for electricity.
Despite high costs, experts say tidal power is more reliable than wind.
The predictable nature of tides makes them an ideal renewable energy source, the journal Philosophical Transactions of the Royal Society A reports.
But finding effective ways of utilising their latent power have proved elusive.