Gaznat was created on the 12^th March 1968 as an engineering consulting firm with the role of promoting the arrival of natural gas in French-speaking Switzerland. In 1974, it became a limited company in charge of supplying natural gas to French-speaking Switzerland. The same year, it started operating its first gas pipeline. Its transport network was then developed in different stages. 

First stage 

Commissioned in 1974, the Gazoduc Swiss Romand (GSR - French-speaking Switzerland gas pipeline) transported gas from Bex (at the end of the gazoduc du Rhône - Rhône gas pipeline) up to Vernier. Its specificity was that it was laid at the bottom of Lake Geneva with landfalls in Vevey, Lausanne-Vidy, Tolochenaz, Gland and La Gabiule (on the commune of Collonge-Bellerive). From there, the gas pipeline crossed the lake again for landfall at Vengeron and finished in Vernier. Another pipeline section on land started in Tolochenaz before connecting at Orbe.

Second stage

In 1977, this first stage was completed on La Gabiule - Annemasse gas pipeline, with a link to the Savoie pipeline owned by GDF SUEZ.   

Fourth stage 

In 1994, Unigaz SA built the Ruswil - Altavilla gas pipeline. In 1995, Gaznat constructed a second sublacustre gas pipeline between Les Grangettes and Gland with landfalls in Clarens, Lausanne-Bellerive and Tolochenaz. In 1998, Gaznat built the St-Julien – Vernier gas pipeline to gain a second entry from France from the Savoie artery. In December 2007, Unigaz SA acquired the high-pressure gas pipeline commissioned by Gansa in 1979 which is used for supplying gas to the Neuchâtel canton as well the regions of Pontarlier and Morteau (France).