This page is more for emphasis than actual fact. The key word here is "correct". The cooling unit needs a precise, CORRECT heat to operate, not just any heat. Too high of a heat will permanently damage the cooling unit. Too low of a heat will cause the cooling unit not to function properly or not to function at all.
A properly operating heat source (gas or electric) will provide correct heat. See Electric Diagnoses or Gas Diagnoses for specific problems or hot wiring for testing the cooling unit.