Tidal energy technologies follow the orientation of tides and can be predicted far in advance. Ocean thermal energy conversion (OTEC) allows the temperature gradient between warmer sea surface water and colder, deep seawater. Generally, this technology requires at least 20°C to function and is thus limited to regions within specific latitudes. Ocean power varies considerably across various regions of the world, for example, wave power is more abundant in northern Canada, southern Africa, and Australia.
The resource potential from marine and hydrokinetic energy is massive, however, costs are still significantly high and the financial environment globally remains hostile. Tidal energy can be almost 10 times more expensive than other more common renewable technologies. These are just some of the factors which have contributed to a fall in ocean energy investments in recent years.
Some technologies have not reached their full market potential yet due to several factors such as uncertainty of returns for commercial investors as well as a lack of evidence of the associated risk. The capacity factor, the amount of power the turbines harvest in comparison to its potential, for such technologies may also not be as high as some more established technologies such as offshore wind. There are also various designs and technologies still being tested to capture the potential of marine energy most efficiently. There can be major differences in technical concept and design and vary in the ways they are oriented and in the manner they convert energy.