Generally, the average use of energy in the United States, per head of population, is about twice as great as in Australia Energy can be saved in every home if we become aware of how much we use. For example, if simple insulating materials are used in building houses, especially in ceilings and walls, the energy used for heating and cooling can be reduced by about a third over the year. As a large proportion of home energy use is for heating water, solar heaters can make a big contribution here. It is possible to link the solar heater with the normal system so that the main's supply is only used to supply what the solar heater cannot do, and this can make big savings.