As of 2000, non-renewable resources (coal, oil, and natural gas) continue to account for a vast majority of our energy sources. Bio-energy accounts for a small part as well; hydroelectric, solar, wind, geothermal, and nuclear energy are all present as energy sources in only minute amounts. Renewable sources of energy are projected to increase dramatically in usage according to all four RCP scenarios; the difference lies with the increased (or decreased) usage in non-renewable sources.