Once the curve peaks, decline is inevitable. The theory is commonly invoked to justify the development of alternative energy sources that are allegedly renewable and sustainable.

Peak Oil theory was originated by American geologist M. King Hubbert. In 1956 Hubbert predicted that US oil production would peak between 1965 and 1970. When production peaked in 1970, it was interpreted as proof that Hubbert's model was correct and that US oil production had entered a period of inexorable and irreversible decline. Unanswered was the question of whether or not US production had declined simply because it had become cheaper to purchase imported oil.

Peak Oil is a theory based upon assumptions. Like other scientific theories, it is subject to empirical corroboration or falsification. Although Hubbert correctly predicted the timing of peak US oil production, several of his other predictions based on Peak Oil theory were wrong.