Alternative renewables are inefficient for the cost  Nuclear power is the most practical renewable energy source as all the others face major difficulties either in scaling up to provide enough to be a major component of nations energy mix, don't provide energy all the time, the 'base load', or cause other environmental problems. Nuclear is a proven technology with large firms that can build large amounts of nuclear energy generation capacity.  The most efficient source of renewable energy has been hydroelectric power, however, this usually creates more problems than it solves. Building a large dam necessarily floods an enormous region behind the dam which in turn can displace thousands of people. There are also enormous ecological costs to dam building. A classical example is the Aswan dam in Egypt along the Nile. Not only did many thousands lose their homes but the yearly inundation of the Nile, which fertilised the surrounding land for thousands of year, was also stopped; the subsequent silting up of the river destroyed much wildlife1. A similar story of ecological destruction and human homelessness surrounded the more recent Three Gorges dam project in China2.  Wind, tidal, and solar power are all affected by issues of reliability. The tendency of wind power, in particular, to be a volatile source of energy, means that other power sources such as fossil fuel power stations have to make up the shortfall when wind levels drop. Tidal power technology is still in at an early stage and may take years to become profitable. It also has the potential to cause environmental problems in the marine environment. For a large area of the European Union, there is not the potential to exploit solar power as there are not enough hours of sunlight.  "Wind and solar power have their place, but because they are intermittent and unpredictable they simply can't replace big baseload plants such as coal, nuclear and hydroelectric. Natural gas, a fossil fuel, is too expensive already, and its price is too volatile to risk building big baseload plants. Given that hydroelectric resources are built pretty much to capacity, nuclear is, by elimination, the only viable substitute for coal. It's that simple."3  1 'Environmental Impact of the Aswan High Dam', 2 'Three Gorges Dam is a disaster in the making, China admits' by Jane Macartney, Times Online 27th September 2007, 3"Going Nuclear A Green Makes the Case", by Patrick Moore, Washington Post. April 16th, 2006: