The assessment is part of an effort by the US Department of Energy to characterize US hydrokinetic waterpower resources including river, wave, tidal, ocean thermal, and ocean current. EPRI completed an ocean wave energy mapping and assessment in 2011.

The assessment analyzed 71,398 river segments across the 48 contiguous states and additional river segments in Alaska. It yielded a total theoretical resource estimate of 1,381 TWh/yr for the continental United States, which is equivalent to approximately 25% of annual US electricity consumption.

The theoretical estimate provides perspective on the magnitude of river resources in the United States. We then broke that number down further to a technically recoverable estimate because there are constraints to developing the resource.

Although the practically recoverable resource is an unknown fraction of the technically recoverable resource, the assessment shows that hydrokinetic generation could be an important renewable energy option for the United States.

—Paul Jacobson, project manager for EPRI’s waterpower research

The results show that the Lower Mississippi region contributes almost half (47.9%) of the technically recoverable resource estimate; Alaska 17.1%, the Pacific Northwest region 9.2%, and, the Ohio region 5.7%. Collectively these four regions represent 80% of the technically recoverable hydrokinetic resource in the continental United States.

By comparison, EPRI’s 2011 wave energy assessment, which calculated ocean wave potential, found an estimated 2,600 TWh/yr and 1,120 TWh/yr of theoretically and technically recoverable resources respectively.

Jacobson also noted that these assessments are a major improvement over estimates for hydrokinetic waterpower resources EPRI completed in 2007, noting that better data and analytical tools are now available that provide a more accurate picture of these resources.