The application of the theory of excessive onerosity in contracts with atake or pay clause inserted in the energy market is still very little explored. The energy market, especially that of free contracting, is quite peculiar. The high volatility of the energy price and the possibility of its renegotiation in the short-term market justify many of the controversies on the subject. By refuting several theories about the legal nature of the take or pay clause, it was shown that, in the case of a pure and simple price clause, the take or pay clause works as a contractual risk management mechanism, but does not represent an assumption of risk in the abstract, only those that could be foreseen by the parties and within a variation reasonably considered if analyzed in the market. Therefore, it is possible to recognize that the theory of excessive onerosity can be applied to contracts with a take or pay clause, especially when the excessive variation resulting from a predictable event allocated between the parties can lead to an extraordinary effect enabler of contractual imbalance and when the variation, not excessive if compared to the market, but sufficient to unbalance the contractual relationship, results from an extraordinary event. The analysis must be made on a case-by-case basis and consider the positive and negative variations in the energy price, from both sides, throughout the entire contractual relationship, not only from the point of view of contractual balance, but also to keep sound the country s interconnected system.