Abstract: An energy conserver for use with a heating and air conditioning unit comprising a three position lock switch selectively moveable between a first, second and third position and a thermostatic control unit including a cooling control switch and a heating control switch each selectively moveable between a first and second position such that the heating and air conditioning unit operates continuously in the cooling mode and heating mode when the three position lock switch is in the first and third position respectively and selectively operates in the cooling or heating mode when within either of two preselected temperature ranges.