Since the disappearance of regulated gas tariffs, individuals must choose between offers whose pricing mechanisms can significantly differ. Fixed or variable price, share of biomethane, evolution of transportation costs: in 2026, comparing only the price per kilowatt-hour is no longer sufficient. The residential gas market is now entirely composed of market offers. To have a comparison point, the Energy Regulation Commission (CRE) publishes every month a Reference Price for Natural Gas Sales (PRVG). This is not a price imposed on suppliers, but a reference allowing consumers to evaluate the contracts proposed. The differences between offers concern not only their price level. In May 2026, the National Energy Mediator listed six fixed-price offers "all included" and sixteen in which only the energy share was fixed. This nuance can directly affect the bill when network costs or certain regulatory components increase. The choice of a natural gas supplier must therefore combine several criteria: price at subscription, evolution formula, fixing duration, origin of the potentially included renewable gas, and quality of tracking tools. ENGIE markets, for example, Gaz Reference 3 years, in which the supply part is fixed for three years and which includes the equivalent of 5% of the consumption in the form of biomethane. The gas distributed in a dwelling comes from a common network: it is therefore not possible to physically bring only the biomethane molecules corresponding to a customer's contract to their home. The principle is based on an accounting equivalence. For Gaz Reference, ENGIE buys a quantity of biomethane corresponding to 5% of the customer's consumption and this quantity is injected into the network. Guarantees of Origin allow tracing the corresponding renewable production. Biomethane is obtained after purification of biogas from agricultural effluents, agri-food residues, organic waste or wastewater treatment plant sludge. Once purified, it can be injected into the same networks as fossil gas. The development of this sector is part of the French energy policy objectives, with a target of 44 TWh of biomethane injected by 2030 included in the energy programming. However, it is necessary to keep the order of magnitude in mind: an offer including 5% biomethane is still mainly composed of fossil natural gas. Biomethane therefore represents a lever for reducing the fuel's footprint, and not a complete decarbonization of heating. The terms "fixed price" cover several realities. Some contracts fix almost the entire commercial price during a given period, while others only fix the supply. In the Gaz Reference 3 years offer, ENGIE fixes the subscription and the price per kWh corresponding to the supply for three years. The components related to transportation and regulatory obligations can, however, evolve. This formula protects the consumer from an increase in the supply cost during the guaranteed period. However, it has the classic counterpart of a fixed price: if market conditions become permanently more favorable, the subscribed price does not automatically decrease. A fixed price therefore constitutes primarily a tool for predictability, and not a guarantee of being systematically cheaper than an indexed offer.