In the energy sector this is the principle of renegotiating the price established in a long term contract, such as the price of natural gas, due to changing market conditions. A price re-opener can be a potential clause in the original contract or a move by one party if he perceives that market conditions have changed drastically. A main disadvantage of price re-openers is that they are difficult to negotiate and may leave one party that needs long term supply out of the contract if the new terms cannot be agreed after for instance the 5 year price re-opener term has elapsed.