Supply comprises all vectors made available to users:
Demand represents the energy needs of users:
As long as supply is not guaranteed to include energy with lower emissions of substances that harm the environment, we will have to use fossil sources, so it is essential to select the vector according to the purpose, always favouring vectors that use less raw materials and have less conversion and transportation losses.
Electricity starts off as water in dams, wind in wind turbines and fossil fuels in thermal power plants. Conversion in these thermal plants entails large losses (50 to 60 %) which are then compounded by losses in the distribution network (10 %). Thus, the electricity used in homes represents only between 30 and 40 % of the (primary) energy used to produce it. However, when burned directly for heating purposes, natural gas has reduced losses, below 20 %.
The use of solar thermal collectors to produce hot sanitary water is another measure to be adopted, because the sun can contribute about 70 % of the total energy needed to produce hot water in each home.