Nexus Energía offers the option to index the price of natural gas to the price of a barrel of Brent crude and to the dollar/euro exchange rate. This has been the historic purchase method, along with the fixed price.
Its main advantage is price stability, since even though it’s an indexed formula, the price only changes four times a year, quarterly.
Formulas indexed to the price of a barrel of Brent and the dollar/euro exchange rate are characterised for simulating the formulas for purchasing natural gas at the point of origin. In those formulas, energy groups reach import agreements with natural gas producing countries via long-term contracts.

Price of natural gas = A+(B+C*Brent603)/TC303

Brent603: Arithmetic mean of monthly prices, expressed in dollars per barrel of Dated Brent and published in the Platts Oilgram Price Report, for the six months before the quarter to which price is applied.

TC303: Arithmetic mean of the daily dollar/euro exchange rate published on the website of the European Central Bank (ECB) for the quarter prior to the quarter in which the price is applied.