Primary energy is the energy that is found directly from nature prior to human induced extraction or transformation. It is a commonly accepted metric for measuring building energy efficiency. The main sources of primary energy include oil, coal/peat/shale, natural gas, hydro, nuclear, and others. These sources are converted into a secondary form of energy which can then be used on site to power the building. The consumption of primary sources is not reflected in a building’s electricity bill. Each primary source has its own conversion rate which varies based on the national electricity grid structure. For instance, total energy consumption in the US in 2016 was 81% accounted for by fossil fuels, whereas France’s dominant primary source was nuclear energy, accounting for 74.5% of the country’s total energy consumption.