Applications of electrofusion joints for gas pipes are increasing and so study on temperature distribution in these joints have an important role in polyethylene welding. The objective of this study is assessment of optimum rate of the conjugate heat transfer in electrofusion joints. The simulations were planned based on Taguchi’s L25 orthogonal array. The thermal lattice Boltzmann based on D2Q9 method was employed to simulate the flow and thermal fields. Signal-to-noise ratios (S/N) analysis were carried out. The flow behaviors and the rate of heat transfer in terms of the Nusselt number have effectively changed by distance, height and radius of electrical wires inside the electrofusion joint. Finally, result analysis verified that Taguchi method achieved optimization of heat transfer rate with sufficient accuracy.