“The chart above shows that fossil fuels yield, on a national average, only a portion of their original energy when converted into electricity. That’s because they are fossil fuels that require other fossil fuels to make the conversion into electricity; their emissions, such as carbon dioxide, also require a lot of energy to be mitigated. Renewables, however, have energy sources that aren’t fossil fuel and their only other energy inputs are production and mitigating the waste from that production. That actually results in more energy produced than fossil fuels put in. Wind, the most efficient fuel for electricity, creates 1164% of its original energy inputs when converted into electricity; on the other end of the efficiency spectrum, coal retains just 29% of its original energy”.
“Energy Points’ methodology measures environmental externalities and calculates the energy it takes to mitigate them. For example, it quantifies the greenhouse gas (GHG) emissions that result from turning coal and natural gas into electricity and then calculates the energy it would take to mitigate those emissions through carbon capture and sequestration”.
“This metric is a more rounded calculation than merely cost or carbon footprint. For example, hydro electricity has the lowest carbon footprint (4 gCO2/kWh), but when Energy Points factors in the full lifecycle of the different fuels, wind is the most efficient”.
Reference:Rani Molla, 2014, The Wall Street journal, “What Is the Most Efficient Source of Electricity?” Retrieved at http://blogs.wsj.com/numbers/what-is-the-most-efficient-source-of-electricity-1754/