Abstract A number of key parameters have been used for defining the efficiency of GTL (Gas-to-Liquids) process. The most commonly used bases are Carbon Efficiency (CE) and Thermal Efficiency (TE). This paper discusses the definition of each of them and the significant developments that have occurred and have been expected on the key focus areas of GTL efficiency improvement. Both CE and TE should be maximized to the extent of technically feasibility and economical justification to ensure responsible and sustainable utilization of natural resources. Nowadays, the GTL technology CE and TE are considered drawbacks of the GTL technology and as a consequence considerable efforts are being made by technology developers to reduce the inefficiencies. The current generation of the GTL technology has a typical plant wide CE of 70–75 % and a typical plant wide TE of 57–61%. Although GTL efficiency is still low compared to conventional refineries and LNG plants, it has been improved significantly over the last two decades. Further improvement can be expected over time as the GTL technology has not gone through the same degree of technological improvement as the conventional system. Advances in GTL technology are projected to increase the efficiency within the next decade as such it would be comparable to conventional refineries and LNG plants that have CE and TE of around 90% and 73% respectively.