Primary energy (PE) is an energy form found in nature that has not been subjected to any human engineered conversion process. It is energy contained in raw fuels, and other forms of energy received as input to a system. Primary energy can be non-renewable or renewable. Where primary energy is used to describe fossil fuels, the embodied energy of the fuel is available as thermal energy and around 70% is typically lost in conversion to electrical or mechanical energy. There is a similar 60-80% conversion loss when solar and wind energy is converted to electricity, but today's UN conventions on energy statistics counts the electricity made from wind and solar as the primary energy itself for these sources. One consequence of this counting method is that the contribution of wind and solar energy is under reported compared to fossil energy sources, and there is hence an international debate on how to count primary energy from wind and solar. Total primary energy supply (TPES) is the sum of production and imports subtracting exports and storage changes. The concept of primary energy is used in energy statistics in the compilation of energy balances, as well as in the field of energetics. In energetics, a primary energy source (PES) refers to the energy forms required by the energy sector to generate the supply of energy carriers used by human society. Secondary energy is a carrier of energy, such as electricity. These are produced by conversion from a primary energy source. PE and TPES are better defined in the context of worldwide energy supply.