Japan is betting a significant chunk of its new generation capacity on energy potential that’s above the ocean. It might do better to invest below.

The country’s territorial waters and Exclusive Economic Zone (EEZ) have an energy potential of 1,326 GW, according to state-sponsored research. That’s almost 30 times more than the size of Japan’s offshore wind program for the next two decades.

Development of technology to tap this energy source has been slow, but test projects are now underway and reaching commercialization in some countries. Japan too has launched a series of demonstration tests of ocean energy. One engineering group has even set a cost target that would make its floating ocean current turbine competitive with several other renewable power sources. Early tests also indicate the energy efficiency of ocean currents is above 40%.

As research on ocean energy grows, so does Japan’s opportunity to get more out of its offshore energy program.