The US Energy Information Agency provides a wealth of data about energy in the US including this 2011 energy flow chart. 82% of energy produced in the US is from fossil fuels. Nuclear is 8%, with renewable energy at 9%.
Many will be startled to see the tiny amount of solar power being produced in the US and that hydroelectric is the biggest source of renewable energy by far. Solar power gets much of the focus for renewable energy but is still a microscopic source of power. Wind power is 6.5 times greater than solar. People say, well, let’s have rooftop solar everywhere, and I agree, it would produce huge amounts of power. But the electrical grid as it exists today can not handle enormous amounts of widely distributed and fluctuating amounts of energy.
New environmental regulations are forcing shutdown or conversion of coal plants to natural gas, which does produce less emissions but is still dirty, especially considering that the gas may be produced by fracking.